Hi guys
You cannot change your username directly. You can ask a god to do it for you, since only they have this power.
However, even though it can be done, it is officially "discouraged". One thing you should seriously consider is the (human) reputation your fellow Monks may have already attached to your current username. Many will not notice the name change, and assume you're a new monk. Is that what you want?
If you just want to be known by a different name, simply go Create A New User (keeping in mind the Site Rules Governing User Accounts). Many people here have done this and it works quite well.
You have to have a really good reason for having your username changed. Simply wanting a new name is not considered sufficient. In particular, the gods will want to be assured that you will never ask for a name change again, and that the requested change will cause minimal disruption to Monastery life. For example, trading a silly, dated, hard-to-remember/type name for an elegant, timeless, easy-to-remember/type name is generally considered A Good Thing; the opposite, not so much.
If you're really certain that you want to rename your existing account, and you've got a really good reason with which to persuade the gods, then /msg your request to them, with your rationale. You'd best be as persuasive (yet humble) as possible. You may subsequently be given the third degree in the Chatterbox.
Thanks for all friends