From inside your Brightspace course,

1.  Select COURSE MENU

2.  Then  select DISCUSSIONS

On the Discussions page, scroll down until you see the tile of the discussion that has been graded. Select the title. For example, the title of the discussion topic in the screen shot below is The "Quarter-Life Crisis",

The first item at the topic of the new screen that appears will be

1. the overall feedback provided by the instructor;

2. the points you earned and letter grade for this discussion;

3. if your instructor has used a rubric, select on VIEW GRADED RUBRIC to view the specific feedback contained on the rubric.