Since you are using an ET-2 tonearm, you will need to get your hands an ET stylus reference gauge, which is just a simple piece of clear plastic the fits over the turntable spindle. The ET stylus reference gauge has a straight line ground in it that runs down the center of it. It's very simple to properly mount a cartridge on an ET-2 arm. Simply install the cartridge as square to the tone arm wand's mounting head as visually possible. Now, place the ET stylus reference gauge on the spindle, flat on the platter, and then loosen the tonearm wand's adjustment screw enough to allow adjustment of the arm. Lower the stylus on to the the stylus reference gauge and adjust the arm wand (length) so that the stylus is always the line, over the arm's full travel, of the stylus reference gauge. You can do this with either the air turned on or off.
Next, in order to make sure the cartridge is dead square to the platter, place a mirror on the turntable platter beneath the stylus. At this point, by looking at the stylus and cantilever in the mirror you can easily see which way to rotate the arm wand to make the cartridge perfectly parallel with the turntable-platter surface. After this step, you should double-check that the stylus location against the stylus reference gauge.
Now you need to level your ET-2 arm. Get your turntable as level as possible with a small spirit level first. Then, with the air turned on, balance the arm by moving the counter weight. At this point, the arm will travel either one way or another. Loosen the arm pivot screw slightly and adjust the small Allen-head set screws to achieve a neutral balance. Before tightening the pivot screw, make sure your arm height is correct for your cartridge height. The arm is level when the arm does not move in or out on it own with the air turned on.
Next, you need to set your VTF with a good scale. Use the correct amount of lead counter-weight to set the VTF so the weight is near the end of the end of the counter weight stem.
Finally, if you have a blank (no groove) record or a test record with a blank section, "play" the blank section to see if the arm travels in or out. Adjust your turntable's feet so that when the blank section played, the arm does not move at all.
BTW, you don't need the ET-2 installation jig to mount a cartridge.
Also, be sure to download the ET-2 manual which will keep you reading for a while. Bruce Thigpen recently taught me the simplified method setting up an ET-2 while visiting his facility in Tallahassee. Thanks Bruce!