Buy and read "Starting Strength" - Ripetoe
Read start here, what is fitness and all of the FAQs
Spend some time looking through the old message board posts and learn how to use the search function. A lot of people just coming to crossfit have the same types of questions most of which have been discussed multiple times so spend some time looking around.
spend $25 and subscribe to the crossfit journal (best subsc. I ever bought) buy back issues of interest.
There is an amazing wealth of information on this site, most of it free. I would say you could easily spend an hour a day for months reading old posts etc. and learn a lot!
If you could find a local CF certified to put you through the basics that would be great.
Do the official crossfit warmup before every workout and Scale your workouts until you get the hang of it.