Bluetooth

How do I make a micro controller control another micro controller through Bluetooth?

You program the first MC to send commands to the second MC. Then program the second MC to react to the commands sent from the first MC.

Weedpharma

You might find this a little more specific about making the connection

http://phillipecantin.blogspot.com.au/2014/01/hc-05-bluetooth-link-of-2-arduino.html

It is then a matter of serial commands, which are the same irrespective of whether they are sent via bluetooth or wire.