Deleting events, or files, or something from iMovie library

I've been trying to delete iMovie projects that I am no longer using. I followed this thread:

https://discussions.apple.com/thread/8047382

but it has not helped. I click on All Events, and there appear to be only two events (ones I actually want to keep). Nothing else is there. But yet, my disk is full because there are tons of projects -- that have nothing to do with these events -- that won't delete!!

I cannot find a folder called "Original Media". When I finally click on ONE clip from ONE project and say "Reveal in Finder", then "Original Media" pops up, but only that clip is in there. I don't want to have to delete hundreds of clips like that one at a time!

I cannot save anything on my computer at all now because all these files I don't need and don't want are stuck on my computer and I don't know where they are and I don't know what I can do to delete them.

This has been incredibly frustrating. Apple: seriously, make projects easier to delete! I may have to stop using iMovie because of this unless somebody can walk me through the process in a way that actually works. HELP!