First, we need to Login with Administrative rights and Windows Authentication in MS-SQL server
Right click on the SQL SERVER Administrator server as shown in below image
Right click on SQL server and click on properties
In Properties window >> Click on security select SQL Server and Windows Authentication mode and click OK
Click on SQL server and Windows Authentication Mode click on the SQL server as shown in below image
Goto Security and there you are going to see a username which is SA
By default, this user is disabled, hence click on properties
Select SQL Server and Windows Authentication mode and change the password
Click on status, here the login for SA user is disabled, so we have to click on enable.
Click on refresh,
After refresh you will see the cross mark on the SA user has been removed.
Restart the SQL server
It will give prompt select yes, once the restart is completed disconnect form the SQL Server and reconnect SQL server Authentication
Type the new changed password here. Click on Remember