How to create an app password?

App passwords are created using your email providers webmail or account settings. Exact steps vary between providers.

Ok, but i was expecting the android app to provide a master password just like the PC version does!?

Ah, ok. If i'm understanding correctly, It sounds like your asking about a lock mechanism that prompts for a password or biometrics before unlocking the app for use. That feature is not currently available within the app. It has been requested by community members on Mozilla connect. You can show support by voting for the idea linked below. https://connect.mozilla.org/t5/ideas/biometrics-to-open-thunderbird-android/idi-p/74741 A community developer has submitted code to add the feature and is in the backlog of changes for review. https://github.com/thunderbird/thunderbird-android/pull/10539 FYI, in the context of email applications, [https://www.historytools.org/docs/what-is-an-app-password-and-when-do-you-need-one-instead-of-your-normal-sign-in "App password" ] is an alternative authentication method used when connecting to your email provider, hence the confusion.