Rule #1: Don't piss off the sound guy!
Have you read the tutorials provided by Rational?
That would be the best place to start.
Get your measurement rig setup-and then start to measure. single cabinets-multiple cabinets-sub and main alignment, delay cabinets and so forth.
Ask LOTS of quesiton (to yourself) about the measurements you are seeing on the screen. Do they make senese? Does you ear hear the same thing? Just because it shows up on a screen does not mean that it is correct.
Take a Smaart class. That would be a big help.
Doing it right takes time-effort-experience-trial and error.
A Synaducon class or 2 or 20 would also be a good thing to consider to get your head wrapped around "this stuff".
Measurement is only a small part of the whole sound equation. Knowing what you should and should not in the system design/layout etc is a HUGE part of the total understanding of what you can and cannot "fix" with what a measurement system shows you.