The OP said he got a new TV but apparently is using the same remote and
the same X1 box. If that's the case, and he's selected the correct HDMI
input using the TV's remote, he should see the output of the box on the
TV's screen. At that point, he should press the Xfinity button on the
remote. That should bring up a menu of choices horizontally along the
bottom of the TV screen. Cursor key to the gear logo and press the OK
button on the remote. Cursor down until the Remote Settings is
highlighted and press the OK button again. Cursor down to highlight the
Voice Remote Pairing and press OK. Follow onscreen instructions.
This should do it because on the instruction sheet that came with my
remote, the text reads, "You'll need to program your voice remote to
control your TV and/or audio receiver's power, volume, and input. To do
this, go to Remote Settings on X1."