Hello @DannyHuang-4387 Please find below the answers to your questions below. Hope this information would help you.
1. We need to frislty on board the application to Azure,
First you need to choose one of the below scenarios that the application (you want to on-board to Azure) is using. More details about these scenarios and code samples for each scenario can be found here: https://learn.microsoft.com/en-us/azure/active-directory/develop/authentication-flows-app-scenarios.
- Build a single-page app
- Build a web app that signs in users
- Build a web app that calls web APIs
- Build a protected web API
- Build a web API that calls web APIs
- Build a desktop app
- Build a daemon app
- Build a mobile app
2. And then our customer need to do some configuration (assuming all our customer has Azure cloud) in their Azure cloud to enable the SSO for this applicaiton.
For this purpose, you would need to configure the application as a Multi-tenant application, so that the application can be accessed by users in other Azure AD tenants. Based on the permissions required by the app in other tenants, a consent might be required to provide by global administrators of other tenants at the first time access to the application and after that all users in those tenants can access the application. For more details, please refer to below documents:
- How to: Sign in any Azure Active Directory user using the multi-tenant application pattern
- Azure Active Directory consent framework
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