use the green UHF key with the black 1 on it.
That is the correct key....however, if you don't have one you can still convert the Blue # 2 remote .
Use the front panel to go to System Info.
Remove the Blue Tab and look down into slot where the tabs go. (you can not simply reverse the tab since it is the wrong configuration for what you want to do)
You will see a guitar pick shaped slider that has about five click stops.
I can't remember if it is the second or third click position (from the left) which puts the remote into a "UHF TV 1" mode...but one of them does.
Take something like a paper clip and click the slider over.
Press and hold the white "sat" button on the top left until they all light up.
Then press the numeral 1....then the pound symbol [#] ....wait 3 blinks....then press the Record button.
If you are in the proper click stop, you will see the Tuner 1 block (box i) change from IR to "IR UHF Pro Band A".
Do NOT put the bottom tab back in as it will change the click position.
If you simply MUST fill the hole, clip the tabs down to nubs that are long enough to stick in the hole, but too short the move the slider.