How to use classic Django app with Django REST framework?
"Normal" Django views (usually) return HTML pages. 
Django-Rest-Framework views (usually) return JSON.
I am assuming you are looking for something more like a Single page application. 
In this case you will have a main view that will be the bulk of the HTML page. This will be served from  "standard" Django view returning HTML (which will likely include a fair bit of JavaScript). 
Once the page is loaded the JavaScript code will makes requests to the DRF views. So when you interact with the page, JavaScript will request Json, and update (not reload) the page based on the contents of the JSON. 
Does that make sense?
I want to use Django REST framework for my new project but I am not sure if I can do it efficiently. I would like to be able to integrate easily classical Django app in my API. However I don't know how I can proceed to make them respect the REST framework philosophy. Will I have to rewrite all the views or is there a more suitable solution?