Select Add clues from files from the Menu button in the Clue Database Manager to add all the clues in a set of files to a clue database.
Select the files whose clues you want to add (hold down Ctrl and click on each file) and press Open. You will then be asked whether you want to timestamp the clues with the date of the files from which they come. If you click Yes the clues will be added to the database in date order, and you will be able to view the date in the Clue Editor when the clue is displayed.