Wis,

Since each ESC has a built in BEC, or voltage regulator, you need to use only one of the BECs to power the receiver. To do this, you simply cut the power wire on one of the ESC's receiver plug. For example, Futaba type wires/plugs use a black wire for ground, a white wire for the control signal from the receiver, and a red wire for the power... this is the red wire that you want to cut on one of your ESCs.

The battery needs to be connected to both ESCs, if you look at my photo of the electronics, you'll notice I have a Y-connector or splitter for the batt connector to power the two ESCs. Both ESCs get their power from the batt, and both ESCs regulate the batt voltage down to about 4.8V on their red receiver plug wire. So, when you cut the red receiver plug wire on one of the ESCs, the other ESC is providing power to the receiver, and the second ESC's BEC/regulator is unused.

Hope that helps!

BTW Futaba uses red/white/black as I described here, but there are other color schemes as well, be sure you know which wire is the power wire on your ESC's receiver plug! When in doubt, check the ESC manual!