To change your nickname, you need to buy the Rename Pass. The pass allows you to change your nickname once; and is spent after use. It can be purchased in the Shop for $18. After the purchase, it appears in the "Special" category of the Garage and disappears once used.
Now a here are a few commonly asked questions:
Q: Does the service maintain all my account information and garage items?
A: Everything (experience, rating, and tanks and guns in the garage) stays the same and only the nickname is changed.
Q: Does the service clean my karma?
A: No, all your violations and the account history are still there.
Q: Does the service change my password as well?
A: No, it will still be the same until you change it.
Q: Does my nickname in the forum and Help Site change too?
Customer support service by UserEcho