1. Head to your creator studio, and navigate to the "Content" page.
2. Click anywhere on the Video you want to un-publish.
Each video's bar (or row) can be clicked anywhere to open the next needed window.
3. To the left of the "Save Changes" button is a 3-dot button. Click that to open additional settings.
4. Click "Make Video Private"
5. Your video will now be reverted back to a Draft state. To confirm this, ensure the video is now showing "Draft Saved".