Luckily, you made a good choice with the Waves line of software plugins. Just about everything you should need is right there.
The enhancers and the like are all just icing. Try 'em out, and if you like them, use them, and if not, then no big-deal.
The compression this plugin offers is truly outstanding as far as software plugins are concerned. For your purposes, though, I would stay away from the compressors and focus your attention on the Ultramaximizer. This tool is for mastering, while the others are more useful for individual tracks. It will quickly become your best friend.
What it is designed to do is boost (maximize) the volume of your work. It really acts like a compressor in that it boosts your quiet parts, and limits your peaks. The beauty is that with a normal compressor, limiting can sometimes sound rather harsh -- like your sound is kind of hitting a brick wall and stopping dead in it's tracks when it hits it's limit (and sometimes distorts during the process).
The maximizer will increase your volume and act as a limiter without the harsh side-effects.
Setting the threshold:
Depends on how loud your music is. You'll want to watch the input meter on the left side, and move the "cursor" up and down untill you find your spot. It's really a combination of your ear and your intuition. The cursor will set your "ceiling," so to speak, where the limiter will kick in. Watch your levels, and ask yourself: "Where on this meter are the levels usually hanging out at?" Does it usually hover around -4, with an occasional jump to -1? If so, then set your cursor at about -4 or -5. You get the idea . . . but play with it. Your ear knows best.
Setting Output Level (meter on the right): For mastering, crank it up as far as it will go without clipping -- Bring it all the way up, and then down just a fraction of a hair.
Hit the okay button, and you're done.
Now your stuff will sound good an loud, like what you hear on the radio and on your CDs.
NO NEED TO USE THE NORMALIZE BUTTON. It's a waste of time, and I've heard advice from many in the know to stay away from it.
C4 :
I forget if it's the C3 or C4 . . . anyhow, this is the multi-band compressor. What this allows you to do is apply all sorts of compression to particular frequency ranges. It's pretty advanced stuff. This kind of tool is great for fixing things like harsh siblances (use it as a de-esser, or if the crash cymbol gets out of hand at times) or plosives ("p" sounds from an overly aggressive vocalist).
Why not just cut the frequency a bit using EQ? You can do that, but suppose that particular frequency is only problematic during certain parts of the song (like cybal crashes or snare hits)? That's where this tool comes in handy, acting as a compressor only for that problematic frequency, while leaving the others untouched.
I could go in to it all, but it would take a while. I would ask for help on these types of things if and when you encounter a problem, because fixing problems is mostly what this tool is for.
Hope this helped.