Uphauling is at the very start of windsurfing. Pulling the sail up and out of the water requires a few basic techniques that are very easy to learn.
First you need to begin by stepping onto the board with the mast base in the center between your feet. The sail should be laying in the water downwind so that it is perpendicular to the board.
When you grab the rope start with your knees bent and your back straight, then use your weight to lift the sail and not your arms. Don't rush, let the sail lift slowly. The water will run off the sail and it will become light.
Climb the rope with small climbs hand over hand, do not lunge forward to grab the sail.
When you are two or three hands away, grab the boom close to the head, you can even grab the mast if it feels easier that way, you should grab first with your front hand and then with your back hand.
When you grab the boom with your back hand, look forward in the direction you want to go. Do not look down at your feet this will throw your balance way off, keep your back hand relaxed and slightly sheeted out for better control (open the back of the sail).
Start with an uphaul rope made for beginners. It will generally be a thicker rope with a few large knobs for better grip.