The Posting Document your Buyer has provided you will be implemented in the Delivery Method tab on the Buyer Contract.
CAKE Basic supports several posting methods including: Email Delivery, POST, GET, XML, SOAP, and JSON. CAKE Basic also supports custom headers if necessary.
Email Delivery: CAKE Basic supports one or more email addresses for the purpose of delivering leads. Custom lead email templates can be made in Set Up > Email Templates.
Note: This example is depicting a POST, that also sends an Email. When both a POST URL and Email Address are configured, the email only gets sent when the lead POST's response is interpreted as a Success.