You can insert a video anywhere you have a text field that support HTML. Look for the small HTML badge in the lower right corner...
Upload your video to a video service that support embedding your video on another page, e.g. YouTube or Vimeo.
For Vimeo you should replace the entire Url in the src-parameter below. For YouTube you only need to change the video id.
Copy the video id from the URL or the share window:
The YouTube video id looks like this: dQw4w9WgXcQ
Copy the embed code below and insert it in a HTML text field in your campaign:
<div class="video show-video"><iframe width="560" height="315" src="https://www.youtube.com/embed/dQw4w9WgXcQ" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>
Insert your own video id in the source-tag:
Save the page and you are done 👍🏻