Tetris Online's press release sums it all up nicely:
WHAT: Tetris Party Tournament No. 4 is the final opportunity for Tetris Party players around the world to win Wii Points™ by demonstrating their competitive Tetris skills. The top 100 eligible participants from each region (North America and Europe/Oceania), based on final ranking, will each qualify to win 1200 Wii Points.
HOW: Participation requires Tetris Party (now available for purchase via Nintendo’s downloadable games service: WiiWare) and separate registration at www.TetrisParty.com/tournament.
Once inside the game, players can connect online by selecting Nintendo® Wi-Fi Connection from the main menu. Then, by selecting “Tournament Deadline: 4/30” from the Tournament menu, players will automatically be placed inside head-to-head matches with other tournament participants in their region. Participants are encouraged to play and win as many matches as possible throughout the entire tournament period to increase their overall ranking.
At the end of the tournament period, players will receive a confirmation code by the game that must be submitted at www.tetrisparty.com/tournament within 12 days after the tournament period ends.
For complete details, registration info, and official tournament rules, please visit www.tetrisparty.com/tournament.
WHEN: Tournament No. 4 Starts: April 16, 2009 at 0:00 (GMT)
Tournament No. 4 Ends: April 30, 2009 at 23:59 (GMT)
WHERE: Online via Tetris Party for WiiWare. Visit www.tetrisparty.com/tournament for more information.
WHO: Tetris Online, Inc.