How can I create SQL database user (for multiple user from one subscription) Microsoft azure

You can either create Login or users for the purpose.
If you create a Login, then the login can access all the databases across that server.
You can use this T-SQL statement to create a Login

CREATE LOGIN readonlylogin WITH password='1234567';

Or you can create a user for the database. The TSQL is

CREATE USER readonlyuser FROM LOGIN readonlylogin; 

You can also set permission to the user by using following T-SQL

EXEC sp_addrolemember 'db_datareader', 'readonlyuser';