Easy Digital Downloads comes with PayPal Standard built in. PayPal Standard is the most basic PayPal account you can get. Settings for it are found under Downloads → Settings → Payment Gateways → PayPal Standard.
The first setting is your PayPal email address. This is the address associated with your PayPal account.
Next you have the option of entering the name of a PayPal Page Style. Page Styles are configured and named at PayPal's web site. Read more about making PayPal Custom Page Styles here.
Once you've created and named a style, you can put that style name into the next field in our settings, called PayPal Page Style.
IPN allows PayPal to communicate with your store, and mark transactions as complete, failed, etc. Normally you want IPN working, but occasionally it can cause issues. and you can turn it off on this PayPal Standard settings page.
NOTE: PayPal IPN verification requires an SSL certificate. See our PayPal SSL FAQ for more information.
If you need to access your PayPal IPN history, see this guide.
The next section needs API keys for Live and Test for:
PayPal API keys allow your store and PayPal to communicate more fully, allowing for more reliable communication as well as some additional features like in-store refunds.