You have to finish the first 5 games (called 5 placements matches) to get in a division …. and depending how you do on them, you will get in a division.
And about the ranking up (your question),
First, you have to win the games to rank up. In league, the most important thing is winning! You win, you rank up, you lose, you rank down.
Second, go for the objects all the time (Insistence in winning). Even if you lose the game, you lose no points (if you were the best in your team)
Third, to get rank up to another division… depending who you face (play against)….if they are masters and you win the game, you will get in the next division.
For example, I was bronze, and I won games, and I still ranking up in bronze… Like I was bronze rank 121, then 103, then 87 …. And then BOOM, I got in a lobby full of Platinums … And I won the game… and I got in Silver…. Then later, I faced a team full of masters and platinums… I won the game, and I got gold…..and so on.