Navigate to Organisation and Users via the Menu.
Click on the + icon next to the organisation in which the Organisation Unit sits.
Expand again using the + icon if necessary until you locate the Organisation Unit (if the Unit sits within another Unit).
Click on the Organisation Unit's name.
Your selection will be confirmed in the breadcrumb trail at the top of the page.
Click on the Details tab.
Click on Delete.
If you still have Users or child Units within the Organisation Unit you are trying to delete, you will see the following popup message.
You will need to Archive/move your Users and/or Archive/move any Organisation Units that sit within this Organisation Unit first.
If the Unit is empty however, you will see the popup message below. Click Yes to confirm the deletion.