To enable your campaign archive, first go to 'Account' within the primary menu. Then, select 'Extras' from the secondary menu. Click on the 'Campaign Archive' menu item. Choose 'Yes' to enable archive of your sent campaigns. Then 'Save' your changes.
You can add campaigns to your archive from the 'Sent Campaigns' page under 'Reports' or from each 'Detailed Campaign Report' page. Learn more about how to add campaigns to your archive.
Enabling campaign archive will also add the archive toolbar across the top of the online view for each sent campaign. Learn more about what's included on the archive toolbar.