TRY CATCH in sql server

How to add try catch in sql server in stored procedure

as

BEGIN

                SET NOCOUNT ON;

                BEGIN TRAN

                BEGIN TRY

                --

COMMIT

                END TRY

                BEGIN CATCH

                       SELECT    ERROR_NUMBER() AS ErrorNumber

                     ,ERROR_SEVERITY() AS ErrorSeverity

                     ,ERROR_STATE() AS ErrorState

                     ,ERROR_PROCEDURE() AS ErrorProcedure

                     ,ERROR_LINE() AS ErrorLine

                     ,ERROR_MESSAGE() AS ErrorMessage;

              ROLLBACK TRAN

    END CATCH