This step has to be done by the App manager.
You can create a custom People category to create an additional filter when searching for people in your org.
- Click your avatar at the upper right hand corner, go to Manage > Manage application > People > People category.
- Select Enable people category.
- Enter the value in People category name singular and People category name plural
- Click Save.
- Click on Add category option and enter the category name.
Once you've created the category, you will see the new field appear in user's profiles, and you can assign the custom category to all users.