There are two main ways to do multi-tenacy with Django sites.
With this approach, one Python process handles traffic for all sites and switches between them based on the Host header.
For users of django CMS, django CMS Multisite is a useful component in this endeavour.
Be aware that with the default setup of Django Multisite and django CMS Multisite you'll get a 404 if the domain does not match an entry in django.contrib.sites, so your configuration will need to be managed carefully.
Please contact Divio support first so we can setup the sub-domains accordingly and give you some pointers.
With separate Divio Cloud projects
This method involves separate Django instances, one for each site. It's generally a straightforward solution, and (for example) avoids some issues with caching at import time.
After you've setup the individual projects, please contact the Divio support so we can make them all use the same database and storage backend.
Because of this setup, you have to remember to push your code changes to all sites and to deploy them all when you make changes.