Take the first session easy. Stand on the gas normal but let off earlier for the corners. Just make sure everything is in working order. Let the engine warm up on the stand for about five minutes before you hit the track. And make sure to stay off the rev limiter.
If the chain is new, it will probably stretch, so double check the tightness after your first few sessions, just make sure its not too loose or too tight. Double check all the nuts and bolts as well on the kart if its new, especially the brakes and steering components.