There's a big blue button on their homepage leading you to the general instance. You pick that. Instances don't matter for most people. If you aren't most peopl

There's a big blue button on their homepage leading you to the general instance. You pick that. Instances don't matter for most people. If you aren't most people, you'll understand what that means by using the platform. As for moderation, Mastodon does have plenty of moderation and federation allows for responsibility to be divided among server/instances owners. If anything, it scales better than a centralised alternative.