When logged in to App.net click the drop-down arrow next to your username in the upper right corner.
Then go to Settings
-> Profile -> Username.
Enter the username you would like to switch to in the first text field, then, enter your password in the second text field.
Click “Change Username” to save.
**Remember you only get one username change during the life of your account. Make it count!
**You are unable to change the username via the mobile app