I'm not quite sure if your trying it out visually or trying to get it to work with a color camera, so I'll just give you a long-winded basic tutorial.
The easiest way to get the feel of ADC adjustment is to first practice visually, preferably with an Alt-Az mount as the horizon reference doesn't change through the night. Since you have one in the NexStar mount, can you put the C8 back on it for ADC testing? ADC use is also easier to learn viewing straight-through (no diagonal) if possible.
Once you have hands on experience getting it to work, you should be able to then figure out how to use it with an equatorial mount and diagonal. Many people have a 'eureka' moment and it becomes second nature even with different scope/mount setups.
A quick exercise first: Attached is an ADC polarity test image with minor color fringing. Some ADC's are made so that in an inverting scope, their levers should be pointing to the left; others should be pointing to the right. There are examples of this issue from more than one manufacturer. Both ways are correct and work equally well--- it's just that this complicates basic instructions. So looking at your computer screen through the ADC (with the ZWO the rotating scale marks should be facing you), start with the levers together and pointing to the left at the mid point of the lever slot overlap. For reference, rotate the scale ring with the white plastic screw also to the left and in-line with the levers and lightly tighten that white screw. Now spread the levers --- the one closest to you down; the other up. Use the white screw and the ring marks as reference to adjust each lever at equal distances from that white screw and try to find a lever position that eliminates the color fringing. *IF* your ADC is correcting the color fringing, it's what I call a 'left hand' ADC. If it's only making the color fringing worse, then simply rotate the ADC body so that the levers are pointing to the right, and adjust the levers to eliminate the fringing. In this case, the closest lever to you should be adjusted up; the other down. If this way works, it's a 'right hand' ADC.
Now onto the real sky--- Assuming Alt-Az and no diagonal with your SCT, point the scope at Jupiter. Insert the ADC into the scope with the levers and white screw together, and with the levers pointing to whatever L or R direction that worked in the above test. Also make sure the levers and white screw are aligned with the horizon as best you can. The ADC should now be at zero correction--- the view would be similar to one without an ADC. Now spread the levers equally from the white screw as in the above test, and you should start to see the atmospheric dispersion cancel out. You should quickly find a best setting for the given altitude, or at least find yourself getting close to a good setting. The better the seeing, the easier it is to find the 'sweet spot'. If you have an eyepiece that's parfocal with your camera, many times the visual setting will be good enough for imaging. If you have a color cam, then you may want to tweak the ADC adjustment using the excellent ADC adjustment tool in FireCapture.
Diagonals complicate matters--- as if not pointed straight up they rotate the apparent horizon, complicating the horizon reference setting. Since diagonals vertically correct the image, they also require you to rotate the ADC--- If without a diagonal your levers were to the left; with a diagonal they should be to the right. Also, with an equatorial mount the horizon reference rotates as the planet traverses the sky. This is why the ZWO ADC has a rotating scale and white reference screw--- so you can update the horizontal reference setting and adjust the levers accordingly from the white reference screw. And remember that the lower the subject, the wider the lever spread to correct the dispersion.
DJ has given you excellent advice for once you're imaging with the ADC. To many people constantly fiddle with ADC adjustment as the planet moves through the sky. When the target is near the meridian, it's not uncommon to be able to go an hour in between adjustments--- after all, even a 90% correct setting is pretty tough to tell from a 100% setting. As a planet is on the rise or on the way down and well away from the meridian, it's altitude changes more quickly and you may find yourself needing corrections every 15 or 20 minutes or so.