HI Tony
Welcome to the site.
If you can supply more details we can give you more specific help as Colin posted.
Not sure of your past modelling experience so apologies if this is teaching you to suck eggs.
Inside your model boat you require:
a motor and coupling to the prop shaft;
an ESC (speed controller) either electronic or a Bobs Board type - basically a moving wiper over some resistance wire driven by a servo;
a rudder servo attached to the rudder;
a receiver;
a motor battery (6v SLA);
a receiver battery if you do not have an ESC with a BEC (battery eliminator circuit).
Outside you need a watertight hull, a rudder and propeller, with a fitted superstructure to keep the insides dry.
Seems like you have the SLA and radio gear.
Cheap pencells for the receiver should get your rudder servo working. Make sure you put the plug in the correct way.
This just leaves the question re the speed controller. Whatever type you have the red wire goes to the SLA ve and the black to the -ve. The other two wires go to the motor terminals, doesn't matter which way but swopping them over will reverse the motor rotation. if you have an ESC there will be a servo type plug and a Bobs Board will have a Servo.
As mentioned ESC's can have BEC circuits so you will not need the seperate receiver battery.
Good luck. Please post how you have progressed 😀

HI Tony,
Pleased you find our site useful, to get the help you require it would be best if you can post photos and some more information about the type of boat you are working with and any specific problems you have. There are many of us that are willing to help where we can, either with direct instructions or with ideas to try.
Best of luck Colin.