Django unambiguously states where to put your models, view functions, forms and the url patterns. Those are grouped into an 'application', which you can have many and define logically by the general task you want them to solve.
Inside the model, view, form and url files (settings too for that matter) you write your code according to the style and philosophy of Python.
For that reason Django can not and must not define for you in what other file should you keep and what name should you assign to some class you write that is required for one of your views or another.
If you don't feel comfortable with the structure of your Django code, it's best to look into general good practices of Python programming, because Django is Python!