Editing Self Check-Out Invitation
The invitation to Self Check-Out can be used as is with the default text and link, but it is easy to customize the message to suit your needs. For example, it's a good idea to include instructions for how guests will pick up any physical items that they have purchased/won.
To edit invitation message:
Go to Site Settings > Customize Your Site > Payments/Credit Card > Self Check-Out Settings.
To edit the Invitation to Self Check-Out email template, go to the Self Check-Out Settings page and click the blue ‘Self Check-Out Invitation’ button to add your desired text. (Be sure to keep the [invite_to_checkout] merge tag in the body of the email, as it generates the personalized link that gives each user access to their cart.)