How do I create/remove a session in Express session?

Question

I'm using Express Session along with Mongo Store. My session is configured so that it stores it's sessions in a Mongo Database. When I visit the app, a new session is being created. I want it so that a session is created ONLY when a user signs up and a session is resumed when the user logs in. I also want to remove a session after 24 days.

This is my configuration code: (I put an actually mongo url when I was testing)

app.use(session({
    secret: "secretakey",
    resave: false,
    saveUninitialized: true,
    store: MongoStore.create({ mongoUrl: "mongourlwenthereintesting", autoRemove: "native", touchAfter: 24 * 24 * 3600 }),
    cookie: { secure: false, maxAge: 1000 * 60 * 60 * 24 * 20 },
    rolling: true
}));