1. Open Community and click the composer at the top of the feed.
2. Choose the Space your post belongs in.
3. Write your post. Type @ to mention a member, they get a notification.
4. Optionally add a cover image and drag it to set the focal point.
5. Click Post.

Cover images are cropped to 16:9 in the feed. Repositioning changes the focal point, not the original file.