The simplest approach is to buy the lock hardware, and the two simplest things you can buy are an "electric strike" and an "electric deadbolt". Google for those two things, they're about $20-300 each depending on quality (strength/security) and are switched on/off with a relay carrying only low voltage (usually 12V or 24V). You will need to choose between fail-secure (locked when no power is applied) and fail-open (unlocked when no power is applied).
You can also buy ZigBee door locks (with touchscreen code entry and ask sorts of fancy features) from Yale and a couple of other vendors, but interfacing with one of those will be quite complex and probably difficult. Also expensive.