Everyone should have received an invitation to the github discussions site, and be able to see the posts there and submit your own posts and comments. If you didn’t get this invitation, it was probably blocked by the email system. Try visiting:
(while logged into the github account you listed on your form).
Once you’ve accepted the invitation, you should be able to visit https://github.com/llmrisks/discussions/discussions/2 (the now-finalized discussion post for Week 1), and contribute to the discussions there.