Answer:
Navigate to Prohibit Software from the Inventory tab. This will list the details of all the software that are already prohibited.
Click Add Prohibited Software. This will open the Add Prohibited Software dialog listing all the software detected in the managed computers. You should have scanned the Windows systems at least once to have the details of the software here.
Select the software that you wish to prohibit and move them to Prohibited List.
Note: In case you have grouped certain software and you are adding that Software