The 'Master Admin Login' is the username generated when you signup for service.
To manage it, go to: Settings --> Account
Enter Username in the 'Username' field
Enter current password in the ‘Current Password’ field
Enter new password in the ‘Password’ field
Re-enter new password in the ‘Confirm Password’ field.
NOTE: Passwords have a minimum complexity requirement:
* Different from login,
* 6 character minimum,
* not use common words or patterns, e.g., 123*, qwert*, voip*, pass* (where '*' is a wildcard),
* contain at least three unique characters,
* contain digits and letters.