sorry to ask obvious questions, but how do you actually use the kite to pull you forwards? what do you you do with the kite relative to the wind? as well, what wind will my 3m pull me on a board.

Sure, 3m is plenty, if you are in strong wind, and on a fast surface (concrete, hard-packed clay / mud, sports field, etc.). Think about a larger kite (5-9 meter) for low wind conditions...