If you need to change the Sign In name for an ESS user, follow the steps below:
Locate the user you wish to change in ESS.
Select Account Settings.
Click Edit on the Sign In Details.
Enter the new Username.
Click Save.
If required, you should now be able to activate the user.
The username can be anything, but if the user is still active, you will need to notify them of the change, as this is what they will now need to use when logging into ESS.
Note: You won't be able to update your own Sign In Name. This is because when you are looking at your own profile, you are using your Member Role and not the Administrator Role. You will need another Administrator to change your Sign In Name.