Following Tutorial 2 we will work with multiple layers to add Images in front of and behind and existing Images. We will use the three Images on the right and below. You can use these Images by clicking on them with your right mouse button and choosing the 'Save as' option. Save the Images to a folder on your computer where you can find them easily.
It is important to work through this exercise because it covers many essential features in The GIMP

Open up the Image of the Coliseum and Zoom into the arches area as I have done on the right. I have used the Navigation Dialog box. You can open up this menu by choosing Dialogs > Navigation from the main menu.
Yo can use the slider to enlarge or reduce your Image or use one of the preset zoom buttons at the bottom of the Dialog box. Once zoomed in you will see a rectangular box inside the Image area in the Navigation Dialog box. This area shows you the area you have zoomed in to. You can drag this rectangle around the Navigation Dialog Image by holding your left mouse button down and dragging it. This way you can pan around the Image whilst zoomed in.

From The GIMP Toolbox choose the Fuzzy Select Tool. Use the Fuzzy Select settings as I have in the Image below.
Click on the black inside of the arch as the image on the right.

You will see a dotted border around the selected area.
The Fuzzy Select Tool works by grouping together similar pixels. The degree of similarity depends on the Threshold setting on the left.

From the menu above the Image choose Select > Invert. This will Select the entire Image except the arch that we originally selected.

From the menu above the Image choose Edit > Copy

From the menu above the Image choose File > New
Use the settings as I have on the right. By default The GIMP will create a new Image the same size and resolution as the Image you have just copied to the Clipboard.
Make sure that you choose the option to Fill with Transparency as I have.

With your new Image active choose Edit > Paste from the menu above the Image. This will paste the Image we copied to the clipboard in step 4.

Notice how the Arch that we selected has a checkered pattern in it. This is displaying the transparent background. We have effectively turned the Arch into a Window.

Before we continue I would like you to save the file. From the menu choose Save Image. Choose a folder where you wish to save the file.
We will save the file as a .xcf file. This is the GIMPs own file format. By saving the file as an .xcf file we will save all the layers and elements, so we can add to them if we re-open the file You can choose the .xcf file format quickly by simply typing the the .xcf after the name in the Save As dialog box. You can also choose the .xcf file extension by using the drop down menu at the bottom of the dialog box.

Choose Dialogs > Layers to bring up the Layers Dialog. Or Choose the Add Tab option in a Dialog box already open and select the Layers Dialog from the menu.

The Layers Dialog box should look like the Image on the left hand side. Right click on the Floating selection and choose New Layer from the pop up dialog box. Double click inside the highlighted blue bar to the right of where it says Pasted Layer and you will bring up the Layer attributes dialog box

Call the Layer Building Layer as I have. Your Layers Dialog box should look like the Image on the left.

Open the Image of the Young man as I have done on the left.
From the menu above the Image choose Select > All

From the menu above the Image choose Edit > Copy

Select The Image of the Coliseum and then choose Edit > Paste

In the Layers dialog box highlight the new pasted Layer and repeat the procedure we carried out in Step 8 to name the Layer.
Next choose Layer > Scale Layer from the menu above the Image. Choose the settings I have used in the Image on the far right.

Select the Move Tool from the Toolbox

With the Move Tool selected, hold down the left mouse button and move the scaled image of the boy over the arch that has the transparent inner area

In the Layers Dialog I have named the Layer with the boy 'Julian Layer' as in the Image to the right.

Place your mouse cursor on the blue area of the Julian Layer and drag it down whilst holding the left mouse button between the Building Layer and the Background Layer. Your dialog should look like the Image below.

You can now see Julian looking from inside the Coliseum, as in the Image on the right.

Now that the Layer is smaller we need to enhance its Sharpness to make it stand out more. With the Julian Layer still selected Choose Filters > Enhance > Sharpen from the menu above the Image

Set the Sharpness settings as I have on the right.

Press the OK button and you will see an improvement to the sharpness of the selected Layer.

Open up the Image of the Vintage Car we saved at the beginning of this Tutorial.

Select the Paths Tool from the GIMP Toolbox.

As we did in Tutorial 2, choose Select > From Path to make a selection from the path. Then choose Edit > Copy from the menu above the Image

make the Image of the Coliseum active. In the Layers Dialog make sure the Building Layer is highlighted as on the right. Then choose Edit > Paste to paste the Image of the Vintage car.

Repeat the procedure carried out in Step 8 and name the new layer Car Layer as below

As in Step 12 we will need to Scale the new layer. Choose Layer > Scale Layer and use the settings I have in the Image on the right.

Use the Move Tool to position the Car as I have done in the Image on the right.
From the menu above the Image choose Filters > Light and Shadow > Drop Shadow

Use the settings that I have used in the Image on the right.

If you look in the Layers Dialog you will see the Drop Shadow on its own Layer as in the Image above

With the the Drop Shadow Layer selected choose Layer > Scale Layer from the menu above the Image. What we want to do is to make the shadow match the other shadows in the Image, so we need to change the shadows height but not its width. Use the settings I have used in the Image on the right.
NOTE: You will have to click on chain to the right of the With Height boxes, when the links are separated this allows you to have a proportionally different Height and Width.

Keep the Layer selected and use the Move Tool to position the Drop Shadow Layer as I have done in the Image on the left.
Hopefully you now have a good idea how Layers work. If you want to keep working on this file make sure you keep the .xcf GIMP file. You can also choose File > Save As and save the file as a Jpeg a Tiff or any of the many file formats available.