Following the instructions at the link below, I successfully built a REST API for my Django application: http://django-rest-framework.org/tutorial/quickstart.
I can
From the screenshot I can see that you want to pass "user" and "password" values to the service. You have send the parameter values in the request header part which is wrong.
The values are sent in the request body and not in the request header.
Also your syntax is wrong.
Correct syntax is: {"user":"user_val","password":"password_val"}.
Also check what is the the content type. It should match with the content type you have set to your service.