Welcome, Moe.
As it concerns GreekChat, the best thing for you to do is to read, read, read all that you can relating to NPHC fraternity membership. You're welcome to participate in any general topics relating to the news, entertainment, chit-chat, etc. But since you are fresh out of high school, there is a LOT you don't know yet about how to navigate Greek life.
To learn more, you should:
1) Exercise discretion. Tell very few people about your interest right now.
2) Visit
http://www.omegapsiphifraternity.org/ and study it from top to bottom. Do not skim it. READ it.
3) Read books like Black Greek 101, The Divine Nine, and In Search of Sisterhood.
4) Meet the members of the fraternity on your campus. Don't just suck up to them -- actually get to know them outside of the fraternity.
Good luck on your quest!