Try to remove the three screws. They my have some thread locker on them so make extra sure the screw driver is the correct size for the screw head slots. A screwdriver blade which is too big or too small will bugger the screw heads. Make sure to put down a large piece of cloth to catch the screw if you drop it. If dropped, they will fall into a black hole and NEVER be seen again! Once the three screws and cover are removed, there is a screw in the center. Adjust this screw clock-wise or counter clock-wise depending upon how the sight post moves. Move the outer adjustment ring with the marks on it so that it is centered on the mark. If you can bore site the rifle and scope, then adjust center screw until aligned. If not able to bore site, a trip to the range is needed. Once the the scope and point of impact match, then replace cover and three screws.