There are many ways to set up and print a greeting card using Photoshop. This tutorial offers a "Photoshop as a layout tool" approach to greeting card printing. If you think of the canvas you will make as the unfolded card (outside or inside), then learning where to place images, text, borders, etc. will be very easy.
Note that there will always be a small white border around on the outside edges of Red River Paper greeting cards . Borderless greeting cards are possible in only certain instances. You must use a 7x10 card and have a 13" wide printer. Special help for that is here