I am trying to access my hosting server’s database through SQL Server Management Studio, everything till login is fine but when I use the command use myDatabase
I believe you might be missing a "Grant Connect To" statement when you created the database user.
Below is the complete snippet you will need to create both a login against the SQL Server DBMS as well as a user against the database
USE [master]
GO
CREATE LOGIN [SqlServerLogin] WITH PASSWORD=N'Passwordxyz', DEFAULT_DATABASE=[master], CHECK_EXPIRATION=OFF, CHECK_POLICY=ON
GO
USE [myDatabase]
GO
CREATE USER [DatabaseUser] FOR LOGIN [SqlServerLogin] WITH DEFAULT_SCHEMA=[mySchema]
GO
GRANT CONNECT TO [DatabaseUser]
GO
-- the role membership below will allow you to run a test "select" query against the tables in your database
ALTER ROLE [db_datareader] ADD MEMBER [DatabaseUser]
GO