Learning about my room and my sound..

Ok, so I have a Radio Shak SPL and I see all these posts on here about people's speakers and performance, now maybe I am an idiot or overwhelmed but how and where do you start to test the performance and synergy of your speakers in your room? I know there are tons of threads but can it be explained to me please?
All I know is I have a SPL that I use to calibrate, and I have a test disc but it is of high tones, so I assume I need a low frequency test disc and then what please>?

P.S. please be kind I know alot of you may laugh at my question but I really want to know what to do
thanks Chad