AIS2011

Hello out there, I am in a small crisis right now and need your help, I am using Express Invoices Plus V3.18 and I am needing to setup the credit card payment gateway. I have done the following. Selected Options, & Credit Card Gateway In the selection area ticked Paypal then when I click options to configure the paypal information I am lost. NEED HELP... API username - under paypal section I put my paypal email address API Password - paypal email password I enter here It then asks for payment Gateway URL ( lost here need syntax to use or help ) Lower down screen it asks about SSL etc token certificate not sure if I need these setup... All assistance is greatful Thanks Andrew.