We are using the official Shopify Subscriptions app, but you may use any other subscription app you prefer. For the Shopify Subscription app, we have in fact some complimentary styling that is inside the theme so the widget you are seeing above can look good.
First, you have to install the app
https://apps.shopify.com/shopify-subscriptions
Then, you should enable it on the product page blocks and adjust a bit the settings.
Finally, you should create subscriptions for your products through the subscription app.
Let me know if you still need assistance with this.
