Traplet Publications has a book called SIMPLY MODEL SUBMARINES
which has good information for the beginner. Otherwise the discussion boards here are a very good source of info.
Some of the basics are:
Get at least a 4 channel radio on a surface or boat frequency for the country you live in.
Generally the radio is set uo like this: left stick up/down is throttle; left stick left/right is ballast control; right stick up/down is dive planes; right stick left/right is rudder. If you have a 6 or more channel radio, use right stick up/down for forward or sail mounted dive planes; stern planes can be controlled by the rotary switch (often used for flaps on an airplane).
Fail safe to empty ballast tank is recommended.
Pitch controller for level sailing is connected to stern plane servo.