To view comments from previous assignments, you can head to submit.cs50.io where you should see a list of all assignments you have submitted. If you click on an individual assignment, you will see a “comments” link that will take you to a page where you can see feedback from your TF.
To be automatically notified of new comments on your submissions, go to “https://github.com/me50/your_github_username”. On the right hand side, you should see the word “watch” (or something similar) next to the star button. Click the watch button and make sure you have “watching” selected so you will “Be notified of all conversations”.