I am not really familiar with Iscrapbook, but most programs will work for you. In order to use 3rd party graphics (not the ones that come with the program or that you can purchase from them) cannot be permanently added to the program.
In order to use 3rd party graphics, you will want to "Insert" the paper or element into your page, just as you would a photo. It is the same process of navigating to the folder in your Mac where the graphics are store, and then selecting which one you want to use.
Thanks for your help.....I am beginning to wonder why in the heck I ever bought this program! I really don't like it at all. But since I am using a MAC, I didn't know what other program would work on it except this one and Mymemories, which I am not too happy with either. Do you know of any other programs that will work on a MAC?