The "Discussions" section is an important part of many project rooms and can be accessed in the room via the rubric bar. New discussions can be created via the action menu ("New entry"). To add a post to an already existing discussion, call up the discussion and select the lowest action "New post" in the action menu. You can also reply directly to a post if posts have already been added to the discussion ("Select action" -> "Answer").
Tip: To prevent your entries from being deleted (by mistake), please select "to be edited by author only" when creating an entry. Then all participants can still reply, but only you and the room moderator can edit or delete the entry.