1. Go to Content
2. Select the unit/lesson where you want to place a link to a(n) Assignment/Discussion/Quiz
3. Click on Add Existing

In the image above we have used an Assignment as an example. Clicking on Discussion or Quiz results in a similar screen with a list of discussion boards or quizzes you have created. 

1. Click on Assignment / Discussion / Quiz
2. Select the desired Assignment / Discussion / Quiz to place a link to it in your content.