Ok, my Newbie friend- we all start somewhere, and you were wise to search out which way to turn, rather than buying g parts which may not work for you.
If you have a suitable motor hooked up, there is step #1. Next, R/C equipment will require a Transmitter(Hand Set) and Receiver(Boat piece), plus An Electronic Speed Controller(ESC).These little units will give you full For/Rev control plus it will take power from your main batteries to power your electronics in the boat. Most all ESC's now have a BEC (Battery Eliminator Circuit), which backfeed 4.5 to 6v to power the Receiver.
Depending on the Voltage required for the motor, will determine which batteries you need.
For simplicity sake, I will assume your motor is brushed, rated for 6v to 8v.- Therefore, the cheaper solution is to use two standard NiMh 7.2v battery packs, wired to keep 7.2volt, with double the amperage storage( if 3000ma each, you would have 6000milli-amp total usable power.) You can modify the wiring for this feature, or I sell the proper wiring couplers to join both battery packs. The Battery pack now plugs into the (+,-) ESC, then plug the ESC motor leads to the motor.- These wires can be reversed if your motor turns the wrong direction per the Tx stick if the Transmitter does not have the Servo Reversing option.
Lastly, you will plug the ESC into the appropriate channel slot in the small Receiver.
Of course, your Rudder Servo plugs into a horizontal stick Rx slot too.
When I supply R/C setups for customers, I also supply custom wiring harness with Fuse, 3 way DPDT switch and Charging Circuit.
Any decent Hobby Shop in your area will steer you right in matching up the proper Radio, ESC and Battery Packs you need or I can also supply all you need.
I have a fully stocked Model Boat Shop, here in New Brunswick, Canada, but I ship parts all over the world.