G'day Peter,
I dont use APT so I cant help you with setup, I've found over the years that youtube is often the best source of information for AP, you may have to discard some of the more hit and miss posts, but if you spend the time searching you will find good post on most AP subjects.
Try this bloke
https://www.youtube.com/watch?v=icd9Tlrb9Jg&t=12s
https://www.youtube.com/channel/UCn3...Cg9J-LQ/videos
he is a good source for beginners and he uses APT.
Beginning in AP is daunting to say the least, there are several books which may help,
Deep Sky Imaging Primer by Charles Bracken
The Astrophotography Manual by Chris Woodhouse
Cheers Russ