Buy a Jewel, Jard, Basix, even a Timney. Throw that one away.
Otherwise. The screw on the back adjusts the sear. The top front is the over travel and the bottom front is the poundage. What I do is adjust the poundage and over travel the way I want them. Then I adjust the sear.
There has to be a video on you tube to give you a better idea of the procedure.