The Polemaster bracket is attached using the existing Bubble Level bracket that came included with your mount and is usually attached to the 'side' via two large thumbscrews.

Remove the 'Bubble' from the silver piece it is attached to with screws, then attach the Polemaster bracket in its place. Attach the Polemaster to the bracket, then the whole assembly to the usual place the Bubble Level or optional Polar Alignment Scope usually attaches to the mount, and you'll be all set!