If you don't have a GitHub account, you should visit GitHub sign-up page to create a new account.
Note that Cornell's enterprise GitHub is not connected to github.com, so you still need to have an account on github.com.
cornell-dti GitHub organization enforces the policy that every
member must have 2-factor authentication properly setup.
You should read and follow the instructions here.
Step 3: Asking a developer lead to add you to
Ask the developer lead on slack.