You must be a Local Administrator to be able to rename an account.
Select System Management, click on Rename Accounts, select the relevant account.
Click on Rename. Enter the new name and click on Save. After logging out and back in, you will see the updated name.
Account names can be 35 characters in length, however we would recommend that you keep them to 20 characters.
Note: You cannot use the '&' symbol in the account name, please use '+' as an alternative.