Digital imaging has made photography editing easier than ever. If you want to add your face to another photo, it doesn't require a professional hand or expensive photo retouching software. The simple copy-and-paste procedure can be accomplished in any basic free image editing program. The trick is to cut as close to the shape of your face as possible to make the effect convincing.
Open the photo of your face and the photo you would like to paste it on in your image editing program. Place your cursor at the top, bottom, left and right of the area in the second, or "destination," photo on which you would like to paste your face. As you do that, look at and note the numeric pixel locations that appear at the bottom of the program window---the left number is the horizontal location, the right number is the vertical location. Subtract the low numbers from the high numbers to obtain the pixel width and height. Do the same to measure the width and height of your face in its photo. Ensure both area measurements have an equal ratio of width to height.
Divide either the width or the height of the destination photo by the corresponding measurement of the face photo to obtain a conversion ratio for resizing. Multiply the full width and height measurements of the face photo by the conversion ratio to obtain the resized dimensions that will make the face photo fit optimally into the destination photo. Select "Resize" under the "Edit" menu. Enter the resized dimensions into the width and height boxes and press "Apply."
Select the "Freeform Selection" tool on the program's toolbar---the tool's icon will look like a dotted-line star or a lasso depending on which editing program you use. Click along the details and contours of your face in its photo until you've enclosed the entire face in a selection. Under the "Edit" menu, select "Copy," then select the destination photo and click "Paste." Click and hold the copied face to move it where it should be in the destination photo. Select the "File" menu and press "Save."
The copy and paste function to place your face in another photo can be achieved in MS Paint, which comes standard with Windows. Other free programs for Windows, Mac and Linux that you can use include Pencil, Helios Paint and GIMP.