I have to work with file upload too. You can begin learning of it here:
- https://docs.mendix.com/studio-how-to/pages-how-to-attach-files (Studio)
- https://docs.mendix.com/howto/data-models/working-with-images-and-files (Studio Pro)
Once a file is uploaded, you can fire a Microflow or Workflow to achieve what you want.