Hi,

You can change the credentials from the user menu if you have admin access rights of the db, if you are normal user you can change it by clicking My Profile in the user menu.

My Profile:

From Users Menu: Settings -> Users & Companies -> Users

Hi,

 Go to Settings then User and Companies and Select Users

From there select the user you want to change the username.

And change the name as shown in the image to change the username.

Hope it helps