Two possible ways of doing it. The first is to build in a platform similar to the factory fitted one. Have a look at a boat already done to see how it is done. This has the advantage of putting the windlass below decks. The second is to cut the anchor locker lid and glass in the aft part to form a platform on top of the deck to mount the windlass. Either way requires a lot of reinforcement to take the loads. You have a choice of vertical or horizontal windlasses - the latter needs more space fore and aft. My 37 uses a Lofrans Cayman, but that might be too big for your space. Lewmar and Lofrans are probably the best makes, although Quick is also popular.