چطوری باید رفرنسشو اضافه کنیم

Error 1 The type or namespace name 'Atf' could not be found (are you missing a using directive or an assembly reference?) c:\users\ali\documents\visual studio 2010\Projects\WindowsFormsApplication10\WindowsFor msApplication10\Form1.Designer.cs 56 17 WindowsFormsApplication10