How to Endorse a Student Question, Answer, or Followup
At the bottom of the post, click the thumbs up labeled: good question.

Or good answer.
The students' instructor-endorsed answer will be labeled in green:
Students will be able to see which questions have an instructor-endorsed students' answer in their feed:
To endorse a followup comment, click the thumbs up button below the post labeled: helpful!
An endorsed followup comment will be labeled in green underneath the comment, and the number of endorsed comments will appear at the top of the Followup Discussions section: