Hopefully this guide will give you a good introduction to using the HM-10 with App Inventor 2. I also hope that this takes you beyond the usual starter guides that do not go past very basic information.
Although I am using an Arduino the principles will be the same for any other microprocessor or indeed for using the HM-10 on its own. Warning: This is going to be a very long post.
To use this guide you should be somewhat familiar with App Inventor, have a BLE enabled Android device, and of course have an Arduino and a HM-10.