The inside wall plate with the 12V outlet and "cable" connector is actually a multifunction plate. I believe it is the third one down in this link:
The little push button--with an LED light--is a signal amplifier used only with the antenna. Don't forget to turn it off when not in use as it does use 12V power. This signal amplifier makes a huge difference and should always be used with an over-the-air signal.
Hook up the TV as you would for cable, push the signal amplifier, raise the antenna, turn on the TV, and turn the antenna 1/4 turn in either direction to optimize the signal.
It's a good idea to tie a bright ribbon, plastic bag, whatever, to the antenna crank as a reminder to lower it down before traveling. Oh, and pivot the antenna back to its original position before lowering it.