If you look at all the connections to the receiver, servos as well you will see they have a red, black and yellow or white color cable. The red and black are the power supplies (Red - Positive, Black - Negative) and the other colour cable is the signal cable.
Inside the receiver all the black connections will be on a common track on the board as will the red for the positive. In this way you can feed your receiver voltage into any connection on the receiver and you can use BEC or Battery Eliminating Circuit speed controllers. They supply the power to the receiver as well as get the signal from it.
If your battery has a 3 way connector on it, only two of the pins will be used and the other is spare.
