Here's a quick step-by-step guide on how to checkout with Four.
Note: If you normally check out with Shop Pay, you may have to opt out of Shop Pay in order to checkout using this method. If you would like to opt out of Shop Pay, you can use the link below to do so. Once you've done that, refresh your browser and try again. Keep in mind, that opting out of Shop Pay will also mean that you will not be able to use the Shop Pay express checkout method on other sites hosted by Shopify.