This feature comes with the paid version of the app. When you purchase the app, this feature will be enabled in your org. After this feature will be enabled in your org, you need to configure it using this link - 


1- When you are configuring the Accounts' Update Form, use the following link - 


2- When you are configuring the Contacts' Update Form, use the following link - 


3- When you are configuring the Leads' Update Form, use the following link -