This tutorial provides instructions for joining communities, posting discussions, and participating in discussions on the RCE portal. To join a community, users click on the community they want to join and then click "Join Community" and "Join." To post a new discussion, users click "Post new topic," add a title and text, and optionally upload a file by browsing and uploading. To participate in a discussion, users can comment on a topic by writing under "ADD COMMENT" and upload documents below the comment text box before saving.