Q:

Problem for creating new user in SQL Server Express

I have SQL Server Express on Windows 10 Pro:

It works fine.I created databases using the default user (Windows user). I need to specify a user ID and password for other purposes.
I did this

but when I try to login using this user id and password, I get this error

I thought it is very easy to add new user. It seems harder than I thought

I also tried to use SA user ID,
I enabled it
and changed the password
Yet I still get this error

A:

It looks like you might have not enabled SQL Server Authentication too in your server during installation. Setup defaults to Windows Authentication only.
See also Login to Microsoft SQL Server Error: 18456.

