You can now sign up and battle with Pokémon from the National Pokédex in the upcoming Ultra No Holds Barred Online Competition with your copy of either Pokémon Ultra Sun or Pokémon Ultra Moon. The competition goes from Friday, May 25, at 00:00 (UTC), until Sunday, May 27, 2018, at 23:59 (UTC). Trainers will be limited to 15 battles per day.
You’ll need a Pokémon Trainer Club account to compete. After you log in, you’ll be able to read and accept the regulations on the PGL. You’ll also need your own Pokémon Ultra Sun or Pokémon Ultra Moon video game and a Battle Team of eligible Pokémon. Accept the regulations on the Pokémon Global Link by Thursday, May 24, at 23:59 (UTC), and get ready to battle! Good luck, Trainers!
All qualified participants in the Ultra No Holds Barred Online Competition will receive 50 Battle Points. Players must complete at least one battle to qualify.
Source: Pokémon Global Link