All Publer needs from you is a link to a native video on the Internet, ending in .mp4, .mov, .webm etc. Native Videos are those Videos that are served to your browser directly and not via a 3rd party player or a video-sharing website.
To get the video url, simply right click on the video and click "Copy Video Address" as shown below. That's the Video URL Publer needs from you. If when you right click don't see the option "Copy Video Address", that video is not native and cannot be processed by Publer. If that's the case, see how you can upload a Video directly from YouTube, Facebook, Vimeo, DailyMotion, Instagram or Vine.
Now you can go back to Publer, paste the URL you just copied into the Video URL field
and finish up your video post. HD (High Definition) version and the HQ (High Quality) version are irrelevant in this case as there's only one version of that Video. Schedule your Video for a specific time in the future or post it right away. Make sure that you're not violating any copyrights or Facebook Policies.
Another example showing all steps: