To directly upload the video to Facebook, access your Video link and choose the "Upload to Facebook" option. If this is your first time, Lumen5 will request for permissions to post on your behalf. To use this feature, you must allow permissions for each of the requests.
You can also choose the "Download Video" option to save the video on your computer, then post it to Facebook manually. When posting on Facebook, you'll see a Photo/Video button, which will allow you to upload your video.