You need a bank account, also get a pay pal account and remember that ebay isn't like amazon, you are buying from people just like you who sell stuff on ebay.
First you create an account with eBay. When you find an item you'd like to purchase click Buy and because it's your first purchase you will need to enter your card details and create a PayPal account. After that it's just like buying from any other website.
Have you tried clicking on one of the Sign Up links? They explain everything.
http://pages.ebay.com/help/account/regis...