Simply slide the micro:bit into the connector on the bat:bit 3 and insert 2 AA batteries and you are good to go!
The bat:bit 3 covers the rear of the micro:bit protecting the test pads from accidental shorts while leaving the reset button and USB connector accessible.
All of the micro:bits edge connector are broken out to another edge connector so you can still use your existing micro:bit add-ons.
There is even a handy little power switch on the right of the board, up is off and down is on!