As per the media registration, I cannot speak directly to the WTE, as I'm new to the whole tea world, but I do have quite a deal of experience with video game, media-only expos. I can probably assume the requirements will be similar.
Usually they require that you proof that you have some form of "published" work when you submit the registration. Sometimes a letter from an editor is enough substantiate one's claims of being media. Sometimes it isn't.
Published work is a very loose concept, however. You could just make a blog, right now, and start posting for a month or two. Afterwards, register with the understanding that you're representing your blog (they usually require a link or address to the outlet you're representing).
If you don't want to go a blog route, and you know someone who already has a blog or writes on tea subjects, you could be potentially allowed in media as a freelancer for that outlet, if your acquaintance will confirm that you indeed will be doing work for them.
I'm probably going a bit off topic here, but my point is that all media means is that you have an asserted effort and passion to write about something. It's amazing how many media get into industry events, or movie screenings, or whatever based on hard work and a nice letterhead.
And the Youtube video thought might not be a bad idea, either. People are increasingly recognizing video creators on Youtube as media.