One of the beautiful things about a mechanical watch is that is requires interaction with its owner to function. That coiled mainspring will only provide power for a day or two (or sometimes longer) if you don’t keep it wound. The automatic, or self-winding, watch, functions as its name suggests.
As long as you’re wearing it, the mainspring maintains tension thanks to the weighted rotor in the movement that oscillates with your arm’s movements. A slipping clutch prevents the spring from getting overwound. Unless you don’t wear your watch daily or you’re an extremely inactive person, you won’t have to wind your automatic. But if you do, just give the crown 20 or 30 spins until the seconds hand starts moving, set the time and then strap it on.