iCloud storage space

I am trying to make a video of a trip I went on. I am making it on iMovie. I am not even five minutes in and its saying "Not Enough Disk Space". Eventually, I came to the conclusion that I must buy more storage because it says I need more. I bought the 50 mega-bite plan, 23.8 mega-bites remain. I think this is perfect and I can continue editing. The same message pops up "Not Enough Disk Space". I have run out of ideas. What can fix this? How? Here what pops up.