You can totally remove the content you have uploaded (it is private and nobody apart from you sees it).

Note: once you delete uploaded footage/image, your draft that contains the removed content will no longer work.

In order to remove unneeded content, please go to the video library, click the 'Uploads' tab, and select 'Videos' or 'Photos' tab:

Then hover your mouse over the video/image you would like to remove and click on a Trash bin icon, that shows up.

Confirm that you would truly like to remove it in the pop-up tab.