If you're just starting out, my absolute best course-management advice is to lay up, and chip on.
Now, since the first sentence has been ignored
, play the ball in the middle of your stance, (ie between your heels), take your stance, grip down on the club, aim for the fattest part of the green, and make a short swing (by short, I mean get your hands just outside your trailing leg, then swing through).
This is usually enough to pop a ball over a bunker. Try your PW, (LW if you've got a good handle on it), and SW if the lie isn't tight (which it probably
isn't, since you're trying to fly a greenside bunker). The SW may be the best bet if the ball is sitting down in the rough (the extra weight will help), but if it's sitting up, the PW or LW will probably do a better job of staying up as well.