FlashCards files are standard video files (MP4 format) and can be uploaded and posted to websites and online services the same way you would with any other video files you may have. For step by step instructions on uploading or posting your FlashCards video to a specific platform/service, here are a few links:
Note: You cannot post to Instagram on a desktop. You have to post using a mobile device.
Note: Facebook defaults to only uploading HD Videos/Photos when on wifi. You will want to change this setting to ensure that your FlashCards Video is posted in HD quality. This can be changed within the Facebook App settings.