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 and demo