ALT-AZ calibration in Celestron software

I use a Celestron AS GT C9.25-S
In the Utilities Menu there is a sub-menu: GET ALT-AZ
Choosing this sub the reading always starts with ALT 90°-AZ 90°, in whatever
the position of the telescope.
There must be a calibration procedure but in the Instruction Manuel I can't
find a clue.
Can anybody help me out?

PS.
I have not been using Newsgroups for many years. What a mess turned this
beautifull medium into!