To set up your first pop-under ad, start by choosing a reliable ad network that supports pop-unders. Create an ad campaign, selecting pop-under as the ad format. Design your ad creatives, making sure they are eye-catching and relevant to your target audience. Set your targeting options, such as location, device, and browser. Determine your bid strategy and budget, then launch your campaign. Monitor your ad performance closely, adjusting your targeting and bid strategy as needed to optimize results. Have you set up a pop-under ad campaign before?