Use your Active Directory credentials to log into Firefly.
If you're accessing Firefly within the school network, you'll be automatically logged in by simply going to the URL you were provided.
Outside of school
When accessing Firefly outside of the school network, you'll need to access the URL provided by your school. You can then enter your Active Directory credentials on the login screen.
Once you're logged in, check out the step-by-step tutorial.