You can upload an existing video file to act as a Baseline Scan by navigating to the Units Page, pressing on the More Button (Aka. "⋮") to open the unit's menu, and selecting "Upload Baseline".
Once selected, a pop up will show up to upload the video.
You may select the file you would like to have uploaded from your file system and click "Upload Video".
Once the video is uploaded in full and shows 100% uploaded, you are done!