In the process of installing SQL Server, the Windows authentication method is the default, and if you want to modify the authentication method after installation, you need to follow the steps below.
1. Log in to SQL Server Management Studio, right-click the database engine and click Properties:
2. In the Server Properties dialog box, click on the "Security" option, and on the right, select "SQL Server and Windows Hybrid Authentication Mode" and click OK.
3. In Object Explorer in Management Studio, turn on server engine-by-bit security-login name.
4. If you do not want to use SA, or if you do not have an SA, right-click on the login name to select "New Login", select "SQL Server Authentication" in the Login dialog box, and enter the password, confirm with OK.
5. Restart the SQL Server service in the services, management tools, Control Panel.
6. Finally, be sure to set the user's status: Double-click the login name under login under Server engine, security, as in part 3rd. Select the status option, and on the right, select "Enable" in "Login" and click OK.
7. Re-open Management Studio, you can use SQL Server authentication mode.
Modify SQL Server login authentication method