If you wish to delete your campaign, all you need to do is click the three dots located at the right side of your campaign dashboard and select Archive.
Once it is archive, you can check that campaign from the Archived page. The campaign will not work unless you un-archive it back.
When you decided to Un-archive the campaign just click the 'Unarchive' button so it will be back to Campaigns page.
If you decided to Delete it totally you can also delete it from the Archived page.