You could PM a staff member about deleting your account, but honestly, the best thing to do is just stop using it and I think it deletes itself. I know your in game account deletes after two years.
As ArcticGalaxy said above, you can send a request to have your account deleted.
Note that this will be permenent and you'll have to wait until a Staff member can approve of the account deletion!
I believe an account is automatically deleted after 18 months of inactivity.
Most of this matter is the server since the Admins rarely deletes accounts nor can we delete accounts on Request. Forum users may deactivate their forum account but the game one will remain until it has been inactive for years. Raz is really the one that works the most with the accounts on the server, but not much work is done directly with deleting accounts since the only one/thing that really does this is the server itself.
Hope this explains it somewhat.