when you installing SQL server you already give password for sa on the Mixed mode, If you are not remember then pls refer in the following points
The default password for the sa login will depend on the version of SQL Server installed and if you are using SQL Express or a pruchased version of SQL Server that we have installed for you. For SQL Server Express users, once you are logged in, please change your password.
SQL Server 2008/R2 Express
User: sa
Password: [blank password - leave field empty to connect]
SQL Server 2012 Express
User: sa
Password: Password123
SQL Server 2008/R2/2012 Web or StandardUser: sa
Password: will be the same as your administrator or root user password at the time the VDS was provisioned.
The default password for the sa login will depend on the version of SQL Server installed and if you are using SQL Express or a pruchased version of SQL Server that we have installed for you. For SQL Server Express users, once you are logged in, please change your password.
SQL Server 2008/R2 Express
User: sa
Password: [blank password - leave field empty to connect]
SQL Server 2012 Express
User: sa
Password: Password123
SQL Server 2008/R2/2012 Web or StandardUser: sa
Password: will be the same as your administrator or root user password at the time the VDS was provisioned.