Configuring your Polycom VVX IP phone to work with SIP.US is quite simple, and can be completed in just minutes!
After logging in as the administrator on your phone (default admin password is "456"), go to Settings -> Lines in navigation bar at the top of your screen. You will then see all the lines this phone has on the left-hand side, and Line 1's configuration settings will show up in the main part of the window.
After choosing which line you would like to configure (likely Line 1), make the configuration page look like this, replacing your Trunk Number and password with the values found under your SIP Trunking tab on SIP.us:
Once you have made the necessary changes to this page, scroll down to the bottom and select Save. At this point, the line you selected on your phone should be active with SIP.US.