If yes, then how? This is on a new account like, made only yesterday
Yes, you can change your username. However, your ELO and GXE for all ladders will reset, meaning you have to start from scratch. How to change: Click on your username on the right side, then choose "Change Name". Then enter the new name you want.
Go to any chat room and type /nick and then it will prompt you to change your username, if it doesn't work, log out and enter a new username and make a new account.