
1 - On the master database, run CREATE LOGIN [App1] WITH PASSWORD = 'p@aaW0rd!'
2 - On DatabaseA, run CREATE USER [App1] FROM LOGIN [App1]
3 - On DatabaseA run ALTER ROLE db_datareader ADD Member [App1]
Reference:
https://azure.microsoft.com/en-us/blog/adding-users-to-your-sql-azure-database/