Right-click folder of interest, select Properties, then select Security tab.  Select "Edit" button to begin.

Select "Add" button.

Select "Advanced" button to locate account.

Select "Find Now" to see list of available accounts

Locate SQLServerMSSQLUser account and hit "OK".

Select "OK" to confirm new account.

Add full control to SQLServerMSSQLUser account, then select "OK" to finish.