To use the shopping cart system, you must set up a Site.ZAPCart page and define the items you wish to offer. Each must have a unique code, a label, and a numeric cost.
Just create the page, and add text like the following:
SK: Survival Kit|7 BT: Basic Training|9.95
That's all there is to it! You can create as many items as you like, and update the information at any time.