Equivalent to storing cookie on Mobile application without browser

I'd like to know the mechanism for storing a secret key on a mobile application for session authentication. I have a Tornado webserver that will use third party external services to authenticate users with E.g. Facebook or Google. I'm familiar with storing cookies using the set_secure_cookie when using a browser. However what if a mobile application is now connecting and doing the authentication. What mechanism would I use to store a secret like a secure cookie for future session authentication? The below shows the code for validating a user:

class GoogleOAuth2LoginHandler(tornado.web.RequestHandler,
                               tornado.auth.GoogleOAuth2Mixin):
    async def get(self):
        if self.get_argument('code', False):
            user = await self.get_authenticated_user(
                redirect_uri='http://your.site.com/auth/google',
                code=self.get_argument('code'))
            # Save the user with e.g. set_secure_cookie
        else:
            await self.authorize_redirect(
                redirect_uri='http://your.site.com/auth/google',
                client_id=self.settings['google_oauth']['key'],
                scope=['profile', 'email'],
                response_type='code',
                extra_params={'approval_prompt': 'auto'})

How would this be modified for a mobile application that doesn't rely on a browser and cookie support?

from Equivalent to storing cookie on Mobile application without browser