programming mecanum

[Noam]

hi, our team is going to use mecanum wheels this year, but I dont really know how to program that
and when I tried to use the code from the examples, (actuators - mecanum drive) but it didn't worked - if I tried to drive forward or backward, so it works (but really bad) and sometimes after a few seconds (after forward / backward drive) so the robot is driving to the side (usually to the right) for 1-2 seconds
any code / advice / tips / etc ?
thanks in advance