Somewhere in the ACP (I forget where now) there is a place to add an accouncement and it has all the forums there, you select which ones you want then add it.
If you're admin, go to your "My Controls" and look at the bottom. You can see an option to make a new announcement. Click it. You can put down info, such as title, beginning date/end date (leave blank if you don't want to use that feature, like GR does). You can also see a menu of your forums. Select the feature "Show all forums" or something like that. Done.
