To close down a vacancy all you need to do is navigate to the vacancy you which to close down.
In the top right you will see the close button and after clicking this you will be prompted to choose a reason for closing the vacancy. Please note that whatever option you choose here will be sent to any candidates that have already applied for the position. This also applies to the message for unsuccessful candidates.
After filling out these you will be brought back to the vacancy dashboard where you will now see the status of the vacancy is marked as filled.