My additions to what others have posted.
1) Using the tools, getting all the hardware set-up and working:
Besides the resources on HTS/other sites, a recent attempt was made by member "omegaslast" , his thread I made a dummy's guide on setting up REW. feedback??
It's nice to have hardware set-up good to go as second nature, so there is no question to the data integrity.
It does NOT get into the specific acoustic measurements taken (the why's, and how to judge). Some of the comments to that thread start that, but I won't comment here.
2) Understanding the tools:
This is the classic "chicken and egg".
My take: get your basic education to the graphs/charts, what they mean.
How to read and interpret them.
The books mentioned and online knowledge is a start.
Then, "jump into it"! start out with your low freq modal/SBIR measurements, understand those - Waterfall charts, and plan/study what corrective action may be needed, etc.
Try to connect the dots between book knowledge and real world, give it time, and ask Q's.
Then move onto your main L/C/R soundstage analysis via ETC and plan/study what corrective action may be needed, etc. Again, ask Q's.
Form another post.
Above all....have fun with it!
Take the approach as a learner and gain knowledge and improvements with your listening room.