A nice easy track is the first bit. Try Hersden in Kent. There's a race there in two weeks time.
Your obviously not going to be jumping anything for a year or two yet so the main thing is to feel comfortable about riding up and over the jumps.
Remember you will fall off a lot but just get up and get back on. Don't let it beat you.
Wear the right gear and don't worry about the bike for a while as the biggest improvements will always come from within.
Lastly remember that it's meant to be fun.