HOW DO I MARK TOPICS AS READ?  I SEE AN ICON THAT INDICATES THIS, BUT CAN'T SEEM TO GET IT TO MARK ANYTHING.  CAN WE MARK TOPICS THAT WE ALREADY READ?

There are two levels of the site's awareness of your travels.
 
When you first access the main page (or return to it by navigating there from one of the lower folders), if there are any new topics posted since you last visited the main page there will be a as opposed to a
Once you have visited the subfolder it will turn back to , whether you actually read any of the new posts or not.
 
Posts that either are new or have new responses added since your last visit have a next to them. The can only be removed by actually reading the post, or clicking the "Mark all topics as Read", which will take you back to the main page. Note that this only marks the post in that folder as read. On the main page, at the bottom there is a link for "Mark ALL posts as read" which does just what it says.
 
HTH