Lynn
Apparently, it works by adding a tiny bit of simulated analog distortion to the signal, which one would naturally get with an analog mixer. At least, that's my understanding. If I'm wrong, then hopefully, someone will set me straight.
I did some analysis of the CE, and found it does two things. First, there is some simulation of non-linearities (distortion) that occurs in analog consoles. With digital, left and right channels have identical characteristics; with analog, slight differences between left and right increased stereo imaging, and distortion also creates higher harmonics that added a very subtle brightness. Second, it seems the CE takes into account input transformers by adding slight frequency response alterations and the distortions typical of inductors in the low end.
As to adjusting the controls, my preferred method is to quick group the controls and experiment. The Drive control introduces the effect itself, while Trim is more about level-matching. However, you can turn the Trim way up to add distortion - I wouldn't recommend this for program material, but it's useful as an effect on individual tracks.
When adjusting Drive, adjust to taste but I'd then recommend backing it off just a bit. The CE is at its best when it adds a subtle effect rather than hit you over the head with it.