All you do is slide the sliders to what you want and try it. What I do is leave the voltages and power target alone and bump up the GPU a little at a time. run something like Unigene Heaven after you bump it and watch your temps and watch for any "artifacting". That's any tearing or glitches. Keep bumping your GPU and rerunning it until you get a glitch. then back off a bit. From there do the same thing for the memory speeds.
Don't go over 90 Celsius on your temp either, that's around the limits that modern GPUs are comfy at.
That's really all there is to it, at least in the beginning. Once you get more experienced, you can mess with voltages and junk, but in the beginning be careful and leave those on auto.
After you get comfy, you can do the same thing and mess with the power target,