Enter your school domain or name or a work email address of someone who works there:
(e.g. "https://www.myschool.org" or "my full school name" or "jsmith@myschool.org")

Alternately, you can follow these manual steps:

1) Find your school domain (i.e. "www.myschoolwebsite.org")
2) Remove the "www." and ".org" or ".com" or ".ca" (i.e. "myschoolwebsite") to get the main part of the domain
3) Append that to bigsis.com to get the Url you need to log in (i.e. "myschoolwebsite.bigsis.com")
4) Type that into your browser and you should be good to go!