A lot of tools on the site require being logged in to use. So, if you'd like a website account, log into the MUSH as one of your characters (sorry, guests can't do this, but feel free to create a throwaway character-- or stick around to chat).
Enter this command: +web/create-account USERNAME=PASSWORD
This will provide a PIN for you to use as you now head over to the registration form to create yourself a login.