Welcome to FCD. Dust off a box and have a seat. Don't mind the spiders.
Sadly FCD is not a thriving thing. However there are some hard liners who can't give it up. I've been here since it launched, it's a neat little thing, and I like my team. Hopefully you will get into a world with some action in it. Far as I know, there are still a few out there.
So you just created a team, I have a good idea what you have on hand as far as personnel... just play exhibition games, don't worry about getting beaten. (Although, I do believe the Ex simulator is kinder to noob teams than actual league play is.) If you don't want to search for teams you can just issue Open Challenges, the sim will match you with any other team that's also issued open challenges. Depending on who's out there, you could end up playing five games in a row against someone at his park... but again, that's not the point. Just feel out the game engine, which kinds of players you want in which positions, which formations you like.
You will likely be thrashed against any veteran team, but right now you're just feeling it out. And once you get into a league, you'll get pounded in your first season until you can rebuild your roster by A/ letting the contracts of your current no-talents expire and B/ signing your own players - which happens in your second season, assuming you've spent the first season building a cash roll to do so.
Yes, when you join a league that's where you'll find new players to sign. Your starter team has 20 under contract, and you can't dump them till after your first season, so right now you have 6 maximum players who you can add, unless you can nicely ask other owners in your new league to take a few benchwarmers off your hands via transfer. When you join a league you'll get the automatic league payout of 4 million bucks. Your current roster is worth a whole lot less than that, probably less than 1 million.