How do you remove an ASSA double cylinder deadbolt?
Without a picture it is hard to tell for sure, but the screws securing the cylinder in place may be under the latch plate on the edge of the door. Remove the 2 screws holding it in place, they should be machine screws, and that will expose 2 more larger had screws and 1 or 2 holes adjacent to the center line of the cylinders. There will be screws in those holes that keep the cylinders from spinning when the key is installed. It will be up to you to to determine what type of driver needed, it changes from lock to lock. Whether it be phillips, straight, or allen. Loosen that screw, partially insert the key so the cylinder does not turn in the keyway and the whole cylinder face should rotate out.