[Answer]-How to manage sessions in django after the user is logged in (without using default admin )?

Django sessions are not tied to the admin. They are enabled by default. They are are provided by a middleware.

The django.contrib.sessions.middleware.SessionMiddleware middleware will populate request.session and request.user on any requests made to your app.

If the user is logged in request.user will be the corresponding User object, otherwise it will be an AnonymousUser instance.

You can find more information in the django documentation. This page includes the different configuration options, but you should be able to make do with the defaults.