SW28,
The best way to use a peep sight is to just look through it without paying any attention to it. Your eye will automatically center in the aperture. Stop looking at it, just look through it! You are too used to looking at the rear sight because you are trying to line up 3 objects (rear sight, front sight, and target). A peep sight basically cuts down the number of objects that you have to line up to 2, the front sight and the target.