Instructions
Select "Multipayer" from the "Call of Duty: Black Ops" main menu.
Select the type of multiplayer game you are trying to play. Choose the available online option if you're using your console's Internet connection. Select "Local" if you're playing offline.
Select "Create a Class."
Choose the class that you have set up that features the MP40. Select the "Primary Weapon" option.
Select "Attachment." Highlight and select "Suppressor." This will add the suppressor attachment to the barrel of the MP40. The suppressor absorbs energy when you fire it, preventing the gun from recoiling during use.