including namespace

hi all, i am new to c#. i have written a class in csharp and i have give the name 'mynamespace' as the namespace name. suppose i want to include the namespace in another .cs file. How can i do that? i have used the keyword 'using' to include that namespace but it gives me the following error during compilation. Inter.cs(6,7): error CS0246: The type or namespace name 'mynamespace' could not be found (are you missing a using directive or an assembly reference?) thanks in advance, msfan