There are a ton of guides out there to help you out. But if you want to win, you're going to have to pick against the Chiefs players at some point.
Good first advice.
You don't need to know every player in the game. You need to know the value of the pieces on the board.
This is, of course, debatable so only take this as a starter guideline, not some manifesto. I, for instance, have never actually won a league. I make the playoffs sometimes but I've never won.
We get the following pieces (think of chess):
1 QB
2 RB
2 WR
1 TE
1 Flex (which can be an RB or a WR, and in some leagues a TE)
1 Defense
1 Kicker
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7 People on the 'Bench'. They can be of any mixture of pieces (positions) as you want. 7 QBs. 7 Kickers. 1 of each. Whatever.
That is how this league is anyway. Those pieces can be changed, but those are the ones we played with. They are fairly standard.
Each week you are up against another player. That is the team you will play. If we play each other, we both pick the best players we can to put into each position.
Then, once the Sunday Day games start, the players are locked in and we sit back and watch if our guys can do a good job or not.
Even if you lose, it can be a bunch of fun to just root for your guys. So I have a WR who plays for Miami and sucks ass? So what. He's my guy.
There's a ton more nuance if you want but it's basically just a game of plugging players into slots, and watching what happens. The best observers are usually the winners, but even if you only observe a little, it can be a ton of fun.