Deleting a campaign is easy, but before you delete you need to be sure that you don't want to keep the content live. If you try to re-publish the same content it will not rank as well as Google doesn't always de-index it. This causes issues with duplication.
With the above in mind it is best to avoid deletion particularly as it can also affect the authority of your subdomain.
Deleting a campaign is a two step process. The campaign itself has to be deleted via the platform and the associated video needs to be deleted from YouTube. For a guide on deleting a video from YouTube see here.
To delete a campaign from the platform first click on "My Campaigns"
Once here choose which campaign you want to delete.
Then you will see a pop-up asking you to confirm.