Synch Xfinity Remote Control with New TV

I got TV and internet (X1) about a year ago. I set up the Xfinity provided remote control to mock my TV's remote. That is, to turn the TV on and off, and to control volume.

I got a new TV, and now the Xfinity remote will no longer adjust volume or turn the TV/Xfinity box on or off. I have to use both remotes now.

How do I reset the Xfinity remote to now work with the new TV? I can't figure this out.