Choose the geometry you want to use: Baerwald (B), Lofgren (L) or Stevenson (S).
Screw the gauge tower on the disc and place the Protractor on the platter. Aim with the pin in the gauge exactly over the pivot point of the tonearm. Move cartridge in the headshell so that stylus lands on the crosslines of your chosen geometry (B, L or S) at step 1 (overhang). In case you cannot reach either point on the Protractor please check your pivot-spindle distance.
Carefully tighten one screw a little bit and make sure you can still turn the cartridge in the headshell. Set antiskating to zero.