Adding a contributor is very easy. Simply go to Editor Activities>Communication Center or find the "Invitation Tool" shortcut on your Quick Start. On this page you can enter a person's name and email and even personalize the email they will receive. That email will automatically create a user account for them and include their login information in the email they receive. This allows them to add and view recipes in your cookbook.
Watch this video tutorial to see how to work with contributors: https://youtu.be/x-1rS6LN4R0