While you have many options for the video file type you choose to share on Facebook, you are subject to restrictions. Videos must not be longer than 20 minutes, and they must be less than 1024 megabytes -- or one gigabyte -- in size. If you have something larger than that which you're hoping to upload to Facebook, you'll have to go back and save it as a smaller file using your video editor.
Review Facebook's guidelines for optimum video size and formats in the Facebook Help Center's "Videos" section. Navigate to the "Uploading and Viewing Videos" section and read the section titled "How can I optimize the quality of my videos?" to get an idea of the best practices for Facebook videos.
Open your video editor, and then open the video you want to work with. If you don't already have your video accessible in your video editing program, import it by selecting "File," "Import," and then select the video from the files and folders on your computer. Drag the video to the Timeline or Storyboard of your video editing program.
Click "File" or "Share," and then "Export" or "Export Movie." This should open up a window that allows you to choose the settings for exporting your video -- which in this case is the settings for making your video smallerto upload to Facebook.
Select the settings that will allow you to save the video in a smaller format than it is now. Some video editing programs provide easy-to-understand selections that include "Small," "Medium," and "Large" export settings. You may also have selections such as "High Quality," "Medium Quality" and the like. From those selections, choose a "Small" or "Medium Quality" setting. If you don't have selections such as those, remember the Facebook guidelines and change your video compression format, dimensions and frame rate to match Facebook's optimum settings.
Give the file a name that will distinguish it from the previous version, and then click "Export." Wait for the video to export, which may take several minutes.