Hey Sprout! We're doing a little work on our tutorial rn, so I'm replying a bit unofficial-like with my personal trainer account. In short, all you have to do next is submit your trainer's reference with our trainer template from our Gallery - you'll find it in the Crater Assets folder - and fill in the required info listed on the template and in the template's description.
Then submit that to the Gallery folder Join Requests. It'll be auto-approved, and we'll double check it to make sure you've filled everything out that's needed.
Once you've been accepted, your Trainer ID will be bumped to the Trainer Registry folder and your ID submission will get a reply from the Professor with a list of Pokemon for you to choose from!