To join, first you have to build your reputation by earning Merits (think of it as karma points).

To build your reputation, you have to contribute to discussions here. By posting helpful guides, tips & tricks or insights of different subjects that benefit people, you'll likely earn them.

From a newbie (your current rank), you'd have to rank up to Jr. Member, followed by Member before being eligible to try applying for some available signature campaigns. And with the other members doing the same, it's a race on who has the highest amount of Merits against limited campaign slots.