You are enrolled in a campaign when you have applied to participate on a campaign and the company has approved you - or when a company has invited you to participate in a campaign and you have accepted this invitation.
Therefore, you are only enrolled in a campaign when both you and the company have accepted it.
You can find your enrolled campaigns when you are logged in, in the menu on the left: Click on "your campaigns".
Here, you will find an overview of all your active campaigns that you are enrolled in and can promote.
Make sure to respond to the applications that companies send you so that your overview is always clear, and you have a good overview of which campaigns you need to address and promote.