Go to the campaigns tab and click 'New'. To duplicate an existing campaign, click the copy icon next to the campaign.
Enter a name for the campaign, and click 'Create'. You can also change the campaign URL if you want it to be different from the campaign name.
Customize the campaign settings. Any settings you set (descriptions, colors, amounts, etc.) are specific to that campaign.
Campaign URL is the campaign identifier used in URL's and Java Scripts (for custom buttons) to open specific campaigns.
For example, if your campaign URL is giving-tuesday, the link will be https://yourwebsite.org/?campaign=giving-tuesday, and the Java Script will be: onclick="Double.openCheckout({campaign: 'giving-tuesday'});"