Register on this blog and become a member of this community by creating your wordpress account.
Use your own name and surname. After registering send an email to firstname.lastname@example.org with your wordpress account. At the beginning you will be registered as a Contributor, that means that you will be able to create posts but not to publish them. The administrator of the site will have to approve them. As in open source projects, if your posts are valuable, you will be promoted to Author. An Author can do everything a Contributor can do and in addition can upload files and publish posts. If you want to do even more, you can ask to become an Editor. More detailed explanation is available here.
It is not mandatory to register in order to participate to the competition.