Navigate to the Library via the Page Navigation Menus on the left, and select Labour Rates.
Find the Labour Rate you want to deactivate/reactivate, select it, and a popup window will appear. To view Inactive Labour Rate, select the SHOW INACTIVE button on the right hand side of the screen.
Here you will see all the details relating to this Labour Rate. 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 Labour Rate to.