On a worm and sector type steering box the sector adjustment screw is at the opposite end of the pitman arm (that's the one that goes to the steering linkage). You should have the steering box centered when you turn the screw in and what your doing is pushing the sector shaft further into the worm gear which in turn removes the excess play, don't make it too tight just screw it it until it's snug then back it out about a 1/4 turn then tighten up the jam nut. Hope this helps.