I cant drag any files to my imovie. It keeps telling me that there is not enough space in the disk. What do I do?

First, check to make sure that you really do have sufficient space in the disk. Go to Apple logo/About This Mac/Storage and check.

If you have sufficient space, then the problem can be fixed by redownloading iMovie. To update/redownload iMovie 10, drag your iMovie 10 app from the Applications folder into the trash, but do not empty the trash. Sign in to the app store and open your purchases folder by clicking on your name at the bottom of the app store side bar. You will see your purchases displayed, including iMovie 10. Redownload/update iMovie from there. If not successful, drag your present iMovie app out of the trash and return it to the Applications folder.

-- Rich