First open the "Document Manager".
Then click on "Edit pages".
Choose the correct page on the right side and then click on the video hotspot icon on the left side. Click where you want to add the element and drag it open.
You can now configure the hotspot on the right side. If you want to use Youtube or Vimeo choose the platform you want under "Source". Then add the ID of the video you want to add. How to get the ID:
If you want to upload your own video, choose "Yumpu" as source and then hit "Select media".
Click on "Upload Files" and choose the video. Then click on "Insert".
That's it! After you hit "Save" the video will be in your magazine.