Select your main image. You may use virtually any image from a photograph or handmade drawing to simple text or a series of images.
Open the photo editing software of your choice on your computer.
Click the "File" menu and select "New."
Enter the desired size of your postcard in the "Image Size" fields. Standard postcard sizes are 4-by-6 inches and 5-by-7 inches.
Click and drag your main image onto the new image file in your photo editing software.
Click and drag the image until it has reached the desired position.
Click "Edit," select "Transform," and click and drag the corners or sides of the image to change its size.
Click "File," select "Save," enter the desired file name and click "Save" to save the main image file.
Open the photo editing software on your computer.
Click "File" and select "New."
Enter the same settings in the "Image Size" field as the main image of your postcard.
Click on the text tool, and select your desired font and size.
Click the text cursor on the lower-right quadrant of the image, and type in your return address.
Click the text cursor on the image, and write any desired information on the left half of the image. Leave this blank if you wish to write information by hand.
Click the line tool, and draw a line down the middle of the image about 1/4-inch from the top to 1/4-inch from the bottom.
Click "File," enter the desired file name, and click "Save" to save the address side of the postcard image.