If you are designing your own card game or a set of cards, you will probably have a basic format that you will use accross multiple cards. In this situation, you will want to save a .SKIN file containing your layout and any custom graphics the cards need.
There are 3 basic types of graphics.
Blanks are the backdrop that textboxes and portrait images are layered over. Custom blanks can be created by importing a .PNG, .JPG, or .GIF image under the "Edit Blanks" menu. Using a .PNG or .GIF with transparent areas for a blank can allow you to have "cut-out" places that portraits can be fitted into. This is especially useful if your Portraits are supposed to be shaped in a format other than a simple rectangle.
Symbols are images that go into textboxes and can be mixed with text. Symbols often represent some kind of energy or element used in your game. Custom symbols can be added under the "Edit Symbols" menu. Symbols should be imported from .PNG or .GIF images with transparency in most cases, as they typically are non-square.
Portraits are boxes containing an image, typically depicting the character, item, or concept that your card represents. Additional portraits can be added under the "Add Part" menu. You can set your portrait to layer behind blanks and other elements of the card, which is useful for when your portrait should go into a "cut-out" area in a transparent .PNG or .GIF blank that isn't a simple rectangle.
Skins don't always need to have a custom portrait set, as each card usually has it's own custom portrait art that will be added when each card is made. However, it is nice to set an image for portraits on your skin as an example and point of reference, especially if you are going to be sharing your skin with others.
Once you have imported all custom blanks and symbols you need and have set up the layout the way you want it, it is time to save the skin and start making cards. Once you finish a card and are ready to make another one in the same format, re-open the skin and start your next card. It is also a good idea to fill in any textboxes in your skin with example text, as if it were a complete card, for a point of reference, especially if you are going to be sharing it with others.
You can save skins under the "Skin" menu.