Look up toward the top-right of the page, right under the ad. You will see a row of yellow buttons (user cp, register, calender, members, f.a.q., search, home, log out); click on the user cp button. That will take you to the control panel for your user. Near the top of the page, you will see a row of links (My vB Home, Edit Profile, Edit Options, Edit Password, Edit Buddy List, Edit Ignore List, Private Messages); click on the Edit Profile link. Then you will come to a page with a bunch of form inputs and such to change a whole bunch of information, and right at the top is where you can change your e-mail address.
Hope I ’splained it well enough for you.
Looks like soccer beat me to it.