1. Login to the web portal with the 'admin' user.
Note: A user with 'basic-write' permissions can do it as well.
2. Navigate to Basic Settings | Management menu and select Change Root Password.
3. Update and confirm the root password.
4. Attempt to connect to the appliance via SSH and confirm that you can successfully login with the new password.
If the web interface is not accessible, open a support request to get instructions for resetting the root password.