how to add a ORCA dll to a ..Net project

Question

I want to add a dll('pborc80.dll) of ORCA software to my C# project. How can I do it? I tried it through 'Add References'. But it's giving me an error. Please kindly solve my problem. It may be a simple one , but please respond to it immediately. Thanking you. Yours sincerely, Vijaya