This video will show you how much air pressure is needed to pump your kite. There is a limit between too much or too little air inside the Leading Edge of your kite. But as a beginner you may want to pump your kite not too hard so you won't explode the Leading Edge of your kite when crashing it hard on the water. But as an advance rider that doesn't crash his kite too often you want to make sure your Leading Edge is Rock solid so the kite can perform at its best.
P.S> You can always use a PSI "gage" but it’s a waste of money and they are not always correct.