You can either just fool around and figure it out, or breakdown and read the User Guide:
http://www.phpbb.com/support/documentation/3.0/userguide/index.php
Note that you can Subscribe to any forum (such as General Discussion) or any topic within a forum and you will be notified of any new posts by email.
To get back to the main Board index, click on the photo in the upper left corner or 'Board index.'
You can upload a picture or text file as an Attachment, then add it to a post, but it will appear inside a scroll box--a bit annoying when trying to view a picture. If you upload a picture somewhere on the Web and use the Img button, then paste the URL address between the Img tags, the photo will be displayed in full size and you can avoid the whole 'upload attachment step' and display the whole picture like God intended.
