SSH in as admin and set a temporary admin password.  I’d recommend ‘admin123’ or something simple since you’ll be changing it very soon

me@linux:~$ ssh -i ~/.ssh/mykey.pem admin@
This system is for authorized use only.
In order to configure your system, please access the Web UI and finish the First Time Wizard.
gw-abe420> set user admin password
New password:
Verify new password:
gw-abe420> save config

Now access the GUI, in this case