Pull down to Open in the pull-down window. Check on the Mailbox square as I have done below. Now Eudora will open the mailbox for this assignment each time you receive mail with that subject. Your first filter is set up. Notice that Filters can do many things and are very flexible.
Filters can also put a copy of a project into a mailbox for a student.
The options can be very time-saving. Close the filter window. If it prompts you for a save, do so.