You can plug the battery into the aux slot to bind.
In fact lots leave it in the aux slot to bypass the receivers internal BEC regulator, it will make the servos slightly faster
The orger of the plugs is, Left to right Batt/Steering/Throttle/Aux. They are maked with a tinyB/S/T/A
the order for each plug is also maked. it is top to bottom.
Hope this helps.