If you are within a Business, Trust, Union or Association record in Redtail, you'll see that there is a Departments widget on the Contact Overview: 

 

 

To add a new Department, just click Add in the upper right corner of the Departments widget.  You'll then see a modal like the below: 

 

 

 

In the Department Name field, enter the Department name, and then enter a Contact Name along with their Phone number and Email or Web address.  Then, click Create Department.  

 

If you want to track multiple people in the same Department for a particular record, you can add as many as you would like.

 

Note: Departmental contacts are not actually contact records within Redtail, so their information is not currently searchable.