Hi!
If you have a only rudder and elevator to control your plane ...you use rudder and then elevator when turning!
If you have aileron,rudder and elevator (like on most trainers and most other airplanes) you use aileron to bank the plane and elevator to turn it. Sooo... when you are about to turn an R/C plane you apply some aileron stick...and then some elevator. The more you bank (use aileron) the more elevator stick you have to apply.

There are some planes that require rudder and ailerons when turning, the bigger they are the more rudder is needed, like big high winged planes like the Piper CUB in 2,5-4,0 m span (not smaller ones though ) but all other R/C planes , scale, low winged warbirds, pattern planes and pylon racers all only need ailerons and elevator to turn.