There is a detailed manual on how to register for an Expo ID, so please refer to it when registering.

Expo ID Registration Manual:
https://www.expo2025.or.jp/wp/wp-content/themes/expo2025orjp_2022/assets/pdf/tickets-index/id_registration_manual_en.pdf 

You can register a new Expo ID via the following link.

Expo ID login/registration:
https://usrmng.accounts.expo2025.or.jp/idmng/users/screen/menuScreen