When you import video into iMovie the first time, iMovie creates a folder on your hard disk called iMovie Drop Box.
You can copy or save video files to this drop box without opening iMovie. To find the drop box folder on your hard disk, go to your home folder/Movies/iMovie Events. In the Finder window, the home folder has the house icon to the left of its name.
Every time you launch iMovie, it checks if there are new files in the drop box and if so, it asks you if you want to import them into iMovie. The drop box is a convenient way to save files to your computer quickly without having to import them into iMovie right away.
To import files from iMovie Drop Box:
iMovie detects if you have new items in the drop box that haven’t yet been imported.
In the dialog that opens, do any of the following:
To add the files to an exisiting Event, select “Add to existing Event” and then choose an options from the pop-up menu.
To create a new Event with the files, select “Create new Event” and then type a name in the text field.
If you’re importing HD video, select “Optimize video,” and then choose Full or Large from the pop-up menu.
The files now appear in iMovie, within the Event you specified at the time the files were imported.