The 2 or 3 THIN wire comming out of the ESC is for the throttle. It will have a connector on the end of it identical to a servo. If that wire has 3 wires going into the plug/connector, you have a BEC (Battery Elimination Circuit ). If it only has 2 wires going into the connector you do not have a BEC and will need a separate battery for the receiver.

The wire from the ESC gets plugged into the throttle channel on the receiver. For Futaba, HiTec and other negative shift receivers, this is USUALLY #3. If there is any doubt check the manual for your transmitter/receiver.

If your wire has 3 leads to the plug you are all set. If it only has 2 leads you will need to plug your separate receiver battery into an unused slot (or "Y" it if all the slots are filled)