If you want to show content from an external website as a popup without a border or extra padding, you can do so by following the steps below.
Create a new display, and from the “Popup” type, select any template.
In the editor, delete all content in the template, and make sure the Form switch is turned OFF.
Click “Add Content” and add an “HTML” element.
Set the iFrame element’s width and height attributes to your preferred values, add style="display:block;", and paste it into the HTML content.
For YouTube, it would look like this:<iframe width="320" height="180" style="display:block;" src="https://www.youtube.com/embed/A85mx5KSHrA" title="Promolayer Debug Guide" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
Go to "Design settings" -> Size & position then:
Enter width value you set in step 4 into width
Set minimum height, margin and padding all to 0.
Switch to mobile preview and set mobile width, height and padding.
Save to finish.