After installing the plugin:

  1. Create a Stripe payment gateway.
  2. Select the gateway in the plugin options.
  3. Register your domain with Stripe and Apple Pay (Simply add your domain here).
  4. Output the button where ever you want using the template tag below.
  5. ???
  6. Profit.

{{ craft.webPayments.button(options) }}

Place this twig where you want the payments button to appear.