If you go to the "GameGuru MAX on Steam" page and select the box "Community Hub" there is some stuff there.
If you go to YouTube and so a search for "GameGuru MAX", their channel will be the first result, broadcasts are every last Saturday of the month 7pm UK time.
I haven't used GameGuru MAX in some time, but from memory there is documentation that comes with the product and can be accessed from within GameGuru MAX, I don't recall where exactly, I do recall Lee saying in a youtube broadcast that it is there - I think I am right in saying that it is one of the screens such as the Hub or maybe the Story Board.
The most active community however is on their Discord server. Sign up to Discord and find their server also named "GameGuru MAX" then join it. You will get much quicker responses to any questions there than anywhere else. There are many channels within their Discord server, please take the time to become familiar with how it all works before posting if you are not already aware of what that entails. If you ask on here(Discord) you will get more accurate answers such as exactly where to find the documentation from with GameGuru MAX or links to specific tutorials/videos etc.
Win 10 Home 64, Intel(R) Core(TM) i5-10300H, 8GB DDR4, NVidia GeForce GTX 1650 4GB GDDR6