From the Newsgroup window, clicking the mouse anywhere on the window while a network operation is in progress will update the information on the screen with the current downloaded information. Once all the article header information has been downloaded and the Newsgroup window is fully populated, the mouse operations are:
Mouse Left Mark/Unmark an article for further consideration
Drag Mouse Left Mark/Unmark multiple articles
Mouse Double-Click Left Select article for viewing
Mouse Middle Toggle the read/unread state of an article
Drag Mouse Middle Toggle read/unread state of multiple articles
Shift Mouse Left Same as Mouse Middle
Mouse Right Reserved for future popup article menu
Mouse Double-Click Right Mark all articles above this one as "seen".