Navigate to the Library via the Page Navigation Menus on the left, and select Competitors.
Find the Competitor you want to deactivate/reactivate and select it, once selected a popup window will appear. To view Inactive Competitors, select the SHOW INACTIVE button on the right hand side of the screen.
Here you will see all the details relating to this Competitor. If you look in the bottom left hand corner of the popup window you will see the Active/Inactive slider. Click on it and set it to the option you want to set the current Competitor to.