...
usr = Users.objects.create(f_name=request.POST['fname'], l_name=request.POST['lname'], s_name=request.POST['sname'], login=request.POST['login'], password=request.POST['password'])
# функция разрушения сессии
drop_user_session(request)
request.session['id'] = ?
request.session['name'] = ?

Users.objects.get...

 
usr = Users(  тута данные )
usr.save()
request.session['id'] = usr.id
request.session['name'] = usr.name