How do I install a Payment Module after Zen Cart is installed?

I installed zen-cart using cPanel and they didnt have a payment module for USA EPAY. I downloaded the USA EPAY file from zen-cart and I am having trouble figuring out how to install it to be added onto the payment module choices. If someone can please assist me, that would be great.

thanks,

David

That mod is SOOOOO Old.

Unless you are running a version of Zen prior to 1.3, I would try to use something else.