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 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.