For certain types of adverts, such as boosting posts, you can create your ad using an existing post that’s already been shared on your Facebook Page. To do this, select the ‘Use Existing Post’ option from the Facebook Ads Manager dashboard. From here, you can choose which Page you’d like to select a post from and pick an individual post from that Page to use as your advert: How to Tag and Track Your Facebook Ads with Google Analytics
How can you create your own video ad? First, understand Facebook video ad requirements including length and video size. We suggest keeping your video as short as possible, even though Facebook allows you to upload a much larger video. Create a video that displays your product or service, and upload directly to the Facebook ads manager by following these instructions.