In this season's code, you would do the following:
Code:
Relay myRelay([slot],[chanel],kBothDirections); //initialize the relay in slot [slot], channel [channel], and allow it to move both directions
myRelay.Set(kForward); //turn the relay on in the forward direction
myRelay.Set(kOff); //turn the relay off
Value and Direction are enumerated in Relay.h in WPILib. Be aware that you cannot Set the Relay as kOn if you use kBothDirections as the third parameter to the Relay constructor.
If this isn't enough detail, just say so.