Every Topspin widget and offer has a unique identification number called a "Campaign ID". To find the Campaign ID for a widget or offer in your account, simply navigate to the relevant section of your account and click the desired widget or offer.
You'll find the Campaign ID clearly displayed on the left side of your widget's basic details:
In this case, the Campaign ID is 10227183.
Although it's not immediately obvious, every email you send in Topspin also has its own unique Campaign ID. To find the Campaign ID of a past email campaign, just click into the relevant email in the Promote section of your account. The email's campaign ID actually appears right in the URL being viewed, as shown below: