In order to add an MP4 file into your Learn system, you will need to first ensure it is SCORM wrapped.
This means it can be successfully uploaded and used by your learners. We recommend that customers use an authoring package, such as Articulate / Stoyline, to import the MP4 and then export as a wrapped file.
If you do not have access to an authoring package and alternative could be to upload the MP4 to Youtube or Vimeo, or another video sharing site and then create the lesson as a URL type. This will allow learners to link directly to that content from the lesson within your Learn system.