You can register if the campaign manager announces that you will accept new participants, but you do not need to do so earlier before the announcement is made. You only need to always monitor the thread and always update if you really want to be part of the campaign, and a few things you might have to do right now are:
- Get notifications from this campaign thread by turning on notifications.
- Always check the thread if you have free time
- Check spreadsheets, maybe there are users at your level leaving the campaign and waiting for the announcement from the manager maybe the manager wants to find a replacement.