This post (and embedded videos) shows you how to set up a webinar page (Clinic Growth only subscribers) or customisable landing page (available in all subscriptions), on which you offer an upsell of a community membership, paid a recurring subscription.
We have used a webinar page to demo but the same principle applies to the Customisable 'Wild Card' Landing Pages.
It shows you the whole process including what your customer sees, and how you manage your members and associated orders.
Before you actually start implementing this, make sure you've already set up a payment processing account with Stripe (it's free), to allow you to process payments. You can find a help video at this link showing you how to do that.
Now watch Part 2 which continues from above and also shows you how to cancel and refund members