Setting the string peep and thr apperture is trial and error.
To shoot with a sight like that, you need to develope a target anchor. Pretty much your thumb lines up under you jaw, and you actuall "kiss" the string. Many tournamemn shooters also used a kisser button as part of their anchor. From there, I used to let the string touch the tip of my nose. This gives a three point anchor and aligns the peepsite in line with your eye. If you tried this anchor style shooting instinctive it is very awkward, but with the sight pin correctly set it is natural and can be as accurate as shooting rifel.
That sight apperture is harder to find than the bow itself, or any bow with the sight alrready mounted.
You can also replace that nylon with a bristle brush rest. I think I may have a couple if you need one.
Also, be careful not to misplace the nylon set screw. Those things are near impossible to find.
Good find.