UCL is Uncomfortable Loudness Level I think and is basically your volume control. Clockwise would turn up the volume. So just set this bottom dial until you can hear comfortably.
The top one seems like if you have the usual ski slope hearing loss then you would dial it more counterclockwise, else if you have more of a flat loss then you’d dial it more clockwise.
Based on your audiogram, which seems to be fairly flat slope except for the 2 dips at 1KHz and 6KHz, I would probably start out the top dial in the middle if I were you because your audiogram has both characteristics (overall flat slope BUT a big dip at 1KHz which is a very critical frequency range). That’s why I’d start out in the middle first, then try to move it either to the left or right to see if you like the new settings better or not.
It’s really pretty simple. Just experiment with the top dial until so find a sweet spot that you like the best and stick to that one. The bottom dial is just the volume dial so set it to wherever you can hear comfortably.