To connect EZPage to your WordPress system you need the WordPress PlugIn from EZPage and the API Key.
Both can be found here:
Settings > Account Information
That's how you do it:
Download the PlugIn from EZPage to your hard drive
Upload it in the WordPress settings under the item PlugIns
PlugIns > Install > "Upload PlugIns" button
Install and activate it
Go to the PlugIn settings and enter your API Key from EZPage there