I just reviewed my first contacts with the greeter's. I was refered to the code of conduct, which I just reviewed again. In the initial contact, I was told to post a public comment and then another greeter entered me into Wikitree. I couldn't find a place to "sign".
Note, if their profile is not viewable, my understanding is that it is difficult for them to be "seen" and approved.
Not sure if any of this is correct, just supposition on based on my experience.