Right after this line:
Code:
RobotDrive drivetrain = new RobotDrive(frontleft,rearleft,frontright,rearright );
You would add code like this:
Code:
drivetrain.setInvertedMotor(RobotDrive.kFrontLeft, true);
drivetrain.setInvertedMotor(RobotDrive.kRearLeft, true);
(or use kFrontRight and kRearRight...just remember to invert both motors on the side!)