Open the Microsoft Paint program on your computer.
Click "Open" and locate the photo you wish to overlay.
Zoom in and use the paintbrush or pencil tool to outline the image. Use a contrasting color to make it easier to see the edges of your image.
Click "Select" and outline the image. Right-click on the image and select "Copy" from the menu.
Click "Open" and locate your background image.
Paste the first image onto the background image. Resize if necessary.
Open the Paintbrush program.
Click "Open" and locate the photograph you'd like to use as the background. Resize if necessary.
Click the "Paste From" option and locate the second photo you'd like to overlay.
Drag, drop and resize the images until you get the desired photo overlay.
Open all the images you want to use in Adobe Photoshop.
Open a new blank canvas -- this will be your background.
Outline the areas of each photo using the lasso tool, magic wand tool or marquee tool. Once outlined, select "Copy" from the "Edit" menu.
Reopen your blank canvas background and paste each image onto it. This will place each image onto a separate layer. Resize, crop and arrange photos as necessary for your overlay project.
Click the "Layers" tab and change the drop down menu from "Normal" to "Overlay." You can also manually overlay images by changing the "Opacity" for each individual layer -- this is also located in the "Layers" tab.