DO NOT USE a board leash
DANGER: You may be tempted to use a board leash to connect you to your board when learning to make it easy to retrieve your board when you come off it. Some kitesurfers use a reel-type leash when they are learning and don't want to lose their board.
However, if you get a serious yank from the kite the leash can unreel until it is taut then your board will get yanked hard towards you, which can cause very serious injuries if it hits you.
DO NOT USE a board leash - practice upwind body dragging to get confidence retrieving your board.
While some experienced wave kitesurfers use a short surfboard leash this is not common or recommended. The leash can also get tangled in your kite lines during a crash or if you get dumped by a wave.