If you are referring to your forum account, this can be done by what the floofs have shown you above. A request will be sent as a confirmation for your forum account to be deleted, however, this is not very effective, as we do not have much time to go searching through accounts and accepting deletion requests. In truth, if you are no longer wanting to use your account, you could simply leave it as it is.
If you wish to delete your in-game account, this is not manually possible by user or staff. If you refrain from logging in for quite a while (some time around/over two years) the server will automatically remove accounts from the server that are not in use. If you wish for your in-game account to be deleted, I would suggest simply refraining from logging in. Hopefully this clears a few things up.