(1) Get (download) a program that grants you access to IRC.
A popular program to do just that is called mIRC - you can download it by clicking here

(2) Configure that program using the "setup" option,  picking an "ident", "nickname", a "real name" (heh), and maybe your email address (not necessary).

(3) Connect to an EFnet "SERVER." #Basketball is on EFnet - the largest "net" in the internet chat world.

(4) Once connected, you type /join #Basketball
Then, you fill the channel with 19 hours of educated basketball opinions each day, 9 days a week. Then, you send cash donations to keep the channel going strong. Then, you get me a job as, um, whoops, sorry, forget that.
 

You can go to IRCHelp.org , which provides more help than you will probably ever need.