Get the Video link from Vimeo
Step 1: Click on share
Step 2: Copy the link like shown below.
Uploading the selected video link into Prismic
Step 1: Click on "Select a link"
Step 2: Choose "Link to the Web..."
Step 3: Insert the link from Vimeo
Step 4: Click on the button "Link to this page"
Step 5: Choose a cover image for the video