How can I add a clip to App Store Connect?

I want that the user can watch a short clip in the App Store before the user decides to download my game in the App Store. I want to upload a clip to App Store Connect but I don't know how to do that. And I get this warning:

To provide metadata for your app clip, you must first upload a build to App Store Connect that contains a clip.

Is it necessary that the user can watch the clip in my game or should the video file just be included in the build even if the clip cannot be watched in my game?

Is it necessary to upload the clip first to YouTube and then paste the URL in App Store Connect?

How can I add a clip to App Store Connect?
 
 
Q