The Exchange Guest Checkout add-on allows your customers to purchase products without having to log in or register on your site.
To allow this option for your customers, you'll want to go into iThemes Exchange > Add-ons and enable the Guest Checkout add-on. To go to the settings for Guest Checkout, click the gear symbol to the left of the Enabled button.
In the settings, you can select whether or not the Guest Checkout is the default checkout option (overwriting either Log In or Register as the default option set in your Exchange settings) and whether or not the Log In or Registration links show.
When your customers check out using the Guest Checkout option, they will enter their email address and then be asked for their billing information (if that add-on or one of the tax add-ons is enabled).
Note: If the product being purchased is a membership product, the customer will be required to register even if the Guest Checkout add-on is enabled.