Log into your account and click on Campaigns & Bid By Domain in the left rail.
Find the campaign you wish to pause and click the green Active button next to it. Select Paused from the dropdown to pause the campaign.
Please note that if you pause a campaign, all content in the campaign will automatically be paused.
To un-pause or set a campaign back live, click on Paused and select Active.
Once you select Active or Paused in the dropdown, the campaigns will automatically update to that status.