Simple Pay/Stripe problem

I linked WP Simple Pay Lite to my Stripe account. I thought once I did that my “Join Here” button would open to a payment page. But it does not. I’m getting the sense that Stripe integration is much more complicated than I thought.

I just want the Pay button to open to a credit card payment page. Can you help me?

The page I need help with: [log in to see the link]