Martin Woolley from the Bluetooth SIG has written some excellent blogs on the subject of using Bluetooth with the micro:bit. His website has some great instructional videos showing how to pair up over Bluetooth on various platforms, and also how to use various demo apps he has written for phones and tablets
You should also check out the Javascript Blocks Editor Documentation.
Handy apps
Bitty Blue, Bitty Data Logger and Bitty Controller
Blocky Talky (for use with app inventor)
NRF Connect which can scan for ther micro:bit and identify running services
Serial Bluetooth Terminal for using Bluetooth UART
droidscript.org and demo