How to change SQL server Authentication mode after install

Here is the code-
DECLARE @AuthenticationMode INT
N'Software\Microsoft\MSSQLServer\MSSQLServer',
N'LoginMode', @AuthenticationMode OUTPUT

SELECT CASE @AuthenticationMode
WHEN 1 THEN 'Windows Authentication'
WHEN 2 THEN 'Windows and SQL Server Authentication'
ELSE 'Unknown'
END as [Authentication Mode]