To join a channel (or a room) type: /join #[channel]
Example: /join #help
To get some information on a user type: /whois [nick]
Depending on your client, it may display this information to a window other than your current active window (such as status). If you cannot find where this information is going, consult your clients help pages.
Example: /whois azca
Join #Help on the IRC network and ask your question