The scenario you've described is a basic example of building a website, which is documented here: Building a Site
Some notes on those instructions applicable to your case:
- Step 1: you can use an existing shell user if you don't want to create a new one. For example if you're using this to serve media for a particular Django application then you might want to use the same shell user that owns the Django application.
- Step 2: use the "Nginx Static Only" app type. You can copy your files into the app directory as soon as the control panel notifies you that the app is ready.
- Step 3: use media.mywebsite.com as the domain.
- Step 4: use
/ as the URI path on the site route. You can also turn on Let's Encrypt at this stage (recommended).
When all of that is done your media will be served from https://media.mywebsite.com/