Hi Bob.
If you’re asking how to completely remove the switch to check it, you’ll need to remove the dash pad (if optioned) and / or then remove the dash bezel screws in order to pull it back from the dash to get access to it for removal.
If you are looking to verify whether you are getting power to the actual antenna itself you can do that by checking the wiring under the dash coming from the switch and then the power at the antenna connector.
They are sometimes finiky. One time mine would not move, after doing the typical things I took a hard rubber mallet and gently tapped on the antenna motor. In parallel I dripped some all purpose oil down the antenna shaft and then it worked fine.
Here’s a picture of the wiring from the Restoration Guide, second edition, pg. #454.