I have never used the payment options myself so not entirely sure how it works but I imagine you'll have to get like a paypal account or some other ecommerce payment "gateway" to use it. Search google for "payment gateway" and you'll probably get a lot of links. I use paypal on my ecommerce sites.

For carts, I don't think you'll need that but I use cubecart which is free and there is also zencart and others out there...if your host has it, check cPanel for "Fantastico"...a lot of hosts offer instant installation of carts.

Try this forum search and see if anything in it relates to you and if not try a different keyword search

http://www.google.com/custom?domains=fo ... %3A1&hl=en