Click on Store Management (This is the 4th option on the left-hand side menu) 

Click on Departments (4th item on the left-hand side menu) 

Select the department you would like to edit from the Department List menu

Revise as needed and click the save changes button. 

Also refer to https://support.petrooutlet.com/en/articles/3520029-how-to-create-a-department for what each option is.

Send POS Transmission to complete the update. 

How to Send POS Transmission :  

http://support.petrooutlet.com/en/articles/3520104-how-to-send-point-of-sale-transmissions