If you have any questions about CAP, such as what the project does or how to get involved, you should read this first. It has all of the rules and the basics of the CAP process. After that, if you have questions, post here with basic questions about CAP. After that, just follow some of the threads being posted the next couple of days: CAP4 is currently in session, so public support is always welcome! Since you're new to Smogon, I recommend just looking at the current project first, and wait until you've become a bit more familiar with the system to contribute. Don't worry, I was in a similar place myself some time ago!
Thanks for the interest, and we hope to see you contribute soon!
- DarkSlay