Practice on the beach or a park. Lay on your back with both feet towards the rail. Pull the mast over the tail and over your head. Practice flying the sail. Then let the sail pull you onto the board. Keep your arms extended. You will learn sail flying and sail control very quickly. When mastered on land, do the same on the water. It's that easy. By the way, I always waterstart with 2 feet on the board. It allows me to come into the board evenly with less knee strain. Good luck!
Make sure the boards on a boardcover without the fin or at least check for rocks so it won't get damaged.