Discussion Board--where is the link?

It's best not to access the discussion boards or the quizzes through those buttons on the left. Far better to go through the icons on the home page. Go to:

1. home page
2. unit 1 folder
3. Unit 1 discussion module
   

When you click the Unit discussion module, it should open to this

Here, I've circled the discussion link in red.
I hope this helps.