When uploading a video you can choose to make it a PreRoll video. This will allow you to select it as a short video commercial to play before your OnDemand Video or Live Stream starts.
Once the video is showing in your videos page you can apply it to either another Video or Event. For Live Events, on the settings page or Videos under Edit Video, use the dropdown menu to select the Pre-Roll video you wish and then choose if you want to display a skip button. This allows your viewers to skip the commercial after either 3,5 or 10 seconds or not at all. Use the dropdown to select the required setting. Once done, don’t forget to save your changes.