In order for you to share someone else's video or file, the owner must first give you permission to do so. When a person shares a video or file with you, they must select either the 'Medium' or 'High' permission level in order for you to be able to share the artifact with someone else.
If you're not able to share an artifact that was shared with you, reach out to the owner and request that they change your permission level!
Want to learn more about sharing and autosharing? Check out our video tutorial here.