There are several features that are accessible from the top of the page. Private Messages are accessible at the top where it says how many messages you have. People can send private messages (kinda like emails) to eachother.
NOTE on Private Messages (PM). You can also send people private messages by clicking on a button that says "PM" by their user name. Be sure to keep up with your private messages and delete old ones. It is possible to overflow your mailbox (a percentage box will keep you up to date).
TIP: Click on "Memberlist" at the top of the page and you will see a list of all available people to message. Just click the PM button, and you are on your way!
Be sure to check out FAQ for more answers!