You can obtain a Zeraora Unite License via in-game mail in Pokémon UNITE by logging on to the game before 2:59pm UTC on August 31, 2021. You will receive a message confirming this after logging on during this period.
If you do not log on during the campaign period, you can still earn a Zeraora Unite License by completing special missions that will be added in future updates.
Please note that planned future missions may be delayed or changed without prior notice.