Add Django apps to existing Wagtail site - django-filer

Question

I've seen a lot of docs explaining how to add Wagtail to an existing Django site, but I'm trying to do it the other way around. I have an existing Wagtail site, and I want to add the django-filer app. I ran the pip install instructions, configured it in base.py, and even created a new app for it where I placed all the files from the git package, but Wagtail doesn't seem to recognized it.

The django-filer file structure is quite different than what I see in Wagtail. I have also tried registering admin models from django-filer but those didn't show up in Wagtail admin so I don't think it's finding the models.

What steps should I do to incorporate it into Wagtail?