Once you have created your campaign that you want to publish in a tab of your fan page, just go to the "Your Campaigns" list and start the publication process by clicking on the "Publish" section.
Go to the "Publish on a Facebook page" section.
After that, choose the Facebook page where you want to publish your tab.
Once the page is chosen, you only have to select in which mode you want to publish your tab, in standard mode or in white label mode. In this case we choose standard mode and the tab will be published. If you choose the white label option, you must follow these steps of white label publication.
Once published you can see the tab on your fan page as administrator.