Hey Angel!
We have an Android installation guide here:
If you're updating, you can place the new .rpa file into the "game" folder shown in the guide, and the delete the old .rpa before booting up!
Saves will carry over automatically, but you can find your saves in "ahitr_storage" if you want to make a manual back up!
Also, welcome back, hope you enjoy catching up with all the new stuff you haven't seen/played!