It can vary slightly but the general process is this:
1) click a link on the website and it takes you to paypal.com (recognizing which site you came from and how much the price to pay is)
2) log into Paypal to access your account
3) select how you want to pay (using money you already have in your account or a credit card/checking account)
4) confirm the payment
Sounds a little more complicated than it really is... Once you have your account set up it is pretty easy.
