Click on Clients on the left side menu

Click on View Client Details in the pencil menu for the client

A slideout window will appear

Scroll to the bottom and click on Add in the Recipients section (or click on the pencil to edit an existing recipient)

A new slideout window will appear

Add the Redtail "ContactID" as the Recipient Code

Select "Redtail CRM" as the data source

Click on Sync