I've been meaning to try Mastodon for a long time (I was never really a Twiiter user). As others have said elsewhere though, I'm not sure where to start. Did you just download the app and join mastodon.social?

I did much less. Just went to mastodon.social in my browser and read what is there. I think you can create an account from there. You can also choose another instance to read and create the account from.