If you're at the district login page, it's just your ID# and password. If you land on a Google login, your username is YourIDemail@example.com. Then it will send you to the district login page, which is your ID# and password.
If it says "You need permission" or "Access Denied" go to the top right of that web page and log out any other users logged in to Google. Then try the link again.