Enable The sa Login in SQL Server

For enabling sa login follow the steps below:

1. In Object Explorer, connect to an instance of Database Engine.

2. On the Standard bar, click New Query.

3. Copy and paste the following example into the query window and click Execute. The following example enables the sa login and set a new password. 

ALTER LOGIN sa ENABLE ;
GO
ALTER LOGIN sa WITH PASSWORD = '<EnterPassword>' ;
GO