Django REST Framework (DRF) is big, as is the concept of building APIs. Some resources you may want to check out:
- The chapter on DRF in Two Scoops of Django is great and worth reading if you have a copy.
- Classy Django REST Framework gives you all the sources you need to see how these views and viewsets work.
- GoDjango has a set of DRF screencasts (part 1, part 2, part 3)
- How Django REST Framework Changed My Life is a good read if you're getting demoralized. :)