Once the Asset Source is created, you can go ahead and generate the Creative Variations. You can generate creative variations in two different ways.
Based on the creative requirements, specify these Layout and/or Companion Banner options in the ‘In-Stream Layout’ section, to override the default layout settings. See Specifying Layouts for VPAID Ads for more details.
Once you're done specifying the layout, click Add new In-Stream Layout. Your layout specifications will be added.
Next, go ahead and click the Update Video button.
In the subsequent screen, click Save Ad.
Your Ad will be saved and you'll be redirected to the Ads and Campaigns dashboard.
You can go ahead and preview the ad by clicking the eye (Creative Preview) icon highlighted above. See Generating Campaign Previews for more details.
Next, you must go ahead and Set up the Campaign.