Activating/deactivating a trigger smart campaign is basically turning it on or off.
In your smart campaign, click the Schedule tab.
Review the smart campaign before activating.
Click Activate.
Be sure the campaign is ready before you click Activate!
From this moment forward, anyone who qualifies for the smart list will go through the flow defined by your smart campaign.
In your smart campaign, click the Schedule tab.
Click Deactivate.
This will stop new people from entering the flow, but people in wait steps or any other flow step will continue to move through the flow until done.