Load this page in the Webflow designer
Select the top portion (grey portion) of a card that doesn't yet have a Video Title
Navigate to the element settings (press the 'D' key on keyboard)
Upload video and wait for transcoding to finish
Publish the site and when it's complete enter Preview Mode and click the 'Load this page' button to the right. (Mac shortcut: ⌘ + Shift + P)
Or open this page from the Publish dialogue.
Follow the instructions on the live website to get the URL's for the video files you just uploaded