Powerline 2000 adding additional adapters

I've got (and love) my Powerline 2000 + Extra Outlet!!  Page 3 of the Quick Start Manual (Getting Started section) says "you can add up to 16 adapters to extend your network". I currently have the one plugged in and connected into my living room wifi/router (through ethernet cable) & the paired adapter plugged into an electrical outlet in my basement - it works great and makes the wifi and ethernet plug-in capability fantastic in that other room. I would like to add another adapter to allow for ethernet wire connectivity in a separate location in another basement room in my house. What do I need to purchase, where can I get it, and how is the connection done?