my idea is changing your username
Here’s how
Way: put new username then confirm then put in password click ok!
If you get a high enough rank, such as mod, you can nickname yourself. Also, this would mess up a lot of things, such as testing applicants.
You can give people nicks with the appropriate plugin. You cannot change the playername in any way, unless you modify your character files manually, but since TShock uses character names for the login details you’d basically be losing your account (unless /login is enabled).
i mean website username
Well… I have seen it done by someone I know. I myself do not know how, and it takes some knowledge. 
cool i just make a new guy call it that name the /login [my username] [my password]