You can currently change your @username both in-game and through rec.net.
Changing your @username in-game
You can change your username in-game by opening your watch, and clicking on your @username to enter a new one.
Please note the warning, you can only change your @username once. Please be extra careful when entering your new @username to make sure there are no spelling mistakes or characters you did not want. Please choose your new @username wisely. We will not be able to change your @username if you have already changed it once.
Changing your @username through rec.net
To change your @username, please visit http://rec.net. Log into your account and navigate to your profile by clicking your profile picture on the top right.
Find the settings cog icon to go into your account settings.
Once you have done that, in this page you will be able to change your @username and nickname/display name. While you can change your nickname or the name that people see above your face up to 3 times a week, you can only change your @username once. Please choose wisely. We will not be able to change your @username if you have already changed it once.