click on a person's name (on the left) and there is a facility to send a personal message (PM) with your email address in it. It is down at the bottom of the page in blue writing.
If you have a PM it will be indicated at the very top of the page in rootschat.
A person must have made three posts to use it, anything will do, hit one of the smileys above, for example and post three separate times.