Within the left side bar under ACCOUNTS, select Store. This will take you here:
Within the horizontal navigation bar, select Products. A drop down will appear. Select Active List. This will take you here:
Select the product that you wish to deactivate. A new page will appear that looks like this:
Select the Settings And Configurations tab. It will look like this:
Within the settings box next to Active, deselect the checkmark to the right.