From April 12 at 6 a.m. PT through April 14 at 11:59 p.m. PT, just start playing the game to enter. The Tetris 99 2nd MAXIMUS CUP is different than the first one, as you don’t have to win first place to score points. Even if you place high during matches, but don’t win, you could still come out on top.
The higher you place at the end of each match, the more points you earn, with every 100 points counting as a TETRIS MAXIMUS. During the week of April 28, the top 999 players with the most event points will be notified, and each will receive 999 My Nintendo Gold Points*.
Source: Nintendo PR