Earlier this week Niantic, the developers of Harry Potter: Wizards Unite launched Code Name reservations allowing existing Pokémon GO and Ingress players to reserve their Trainer and Agent names.
Existing Pokémon GO and Ingress players have until April 30th, 2019 at 11:59 P.M. PT to reserve their Code Name.
Unfortunately for Pokemon GO players that sign-in using Pokemon Trainer Club will not be able to make a reservation, first you will need to link your Google account to your Trainer Club account.
There may be some cases where Code Name reservations are not guaranteed. For example, your Code Name may overlap with a user in another Niantic title. For this scenario, reservation will be first come, first served so make sure you reserve your name as soon as possible.
If you have the same username on both your Pokémon GO and Ingress account, you only need to reserve your Code Name once.