Where can I enter my app specific password on appcenter.ms testflight integration?
You can follow the instructions here: https://docs.microsoft.com/en-us/appcenter/distribution/stores/apple#adding-two-factor-authentication
Specifically:
Adding Two-factor authentication
If your Apple account has two-factor authentication enabled, App Store Connect requires an app-specific password as security. You can add an App-specific password to your account by navigating to Developer accounts in your Account settings.
- Hover over an item in the Accounts list.
- Click the three vertical dots on the right side of the list
- Select Update app-specific password.
- Generate an app-specific password using the Apple ID portal.
- The name is for you to remember which service or app is using the app-specific password.
- Copy the generated app-specific password and paste it into the dialogue.
- Save by clicking Update.