Browse to the component in Joomla's backend. In Joomla's toolbar area (top right), you'll see “Parameters” for Joomla 1.5 or “Options” for Joomla 2.5. Click the button to open the configuration window.
The parameters are pretty straight forward. Hover over the label in the component's parameters/options to see a detailed description of each field. Below are a few notes on select ones.
Mode – This determines whether the button should post to PayPal's live site (Live) or sandbox (Test). Remember that you will need to use a sandbox seller account if you are using PayPal's sandbox to test out EzPPb.
Merchant IDs - There are three entries for merchant IDs: default, cart, and sandbox. These can either be your PayPal email or merchant ID (email is required for encrypted buttons). The default merchant ID prepopulates the merchant ID for new buttons. You can define a different merchant ID for the built-in cart although this is not required as it will use the default merchant ID if left empty (one or the other must be filled in order for the cart to function). The sandbox merchant ID allows you define a merchant ID to use for testing. If the mode is set to test, EzPPb will use this ID instead of the button's set ID. To obtain a sandbox merchant ID, you'll need a PayPal developer account.