1st time:

1. window authentication login first
2. After that, right click server and click properties
3. security: change the login method (SQL Server Authentication actually also allow window authentication)
4. restart

Restart SQL Server service:

1. Open SQL Server Configuration Manager
2. Expand SQL Server Services
3. Right-click SQL Server (MSSQLSERVER) or SQL Server (SQLEXPRESS) → Restart

set sa account:

1. expand the server, expand security, expand logins
2. right click sa, click properties
3. set password, set status enable login
4. restart

add account:

1. expand the server, expand security, expand logins