When you select a library or an event in the Libraries list, the clips in the library or event appear in the browser.
You can scroll through items in the browser, and you can sort events and clips to make it easier to find the ones you want. You can also search for specific clips and show or hide clips based on their rating.
In the iMovie app 
on your Mac, do any of the following:
Sort events by name or date: Choose View > Sort Events By, and choose an option from the submenu.
Sort clips by name, date, or duration: Choose View > Sort Clips By, and choose an option from the submenu.
In the iMovie app on your Mac, select an event in the Libraries list.
In the browser, click the pop-up menu to the left of the search field and choose one of the following:
All Clips: Shows all clips in the event you selected.
Hide Rejected: Shows only clips you haven’t marked as rejected.
Favorites: Shows only clips you’ve marked as favorites.
Rejected: Shows only clips you’ve marked as rejected.
You can show events from all of your open libraries.
In the iMovie app on your Mac, select All Events in the Libraries list.
You can search for clips and other media by name or media type. For example, you can search for the name of a clip, or for “photo” or “video.”
In the iMovie app on your Mac, select an event in the Libraries list.
In the browser search field, type part or all of a name or media type you want to search for.
The browser displays clips whose name or media type matches the text you typed in the search field. To display all clips again, clear the search field.