Most likely, you are talking about Newtonsoft.JSON:
http://json.codeplex.com[
^].
If so, just look at the title:
CodePlex says:
Json.NET
Json.NET is a popular high-performance JSON framework for .NET
It is not supposed to be anything like COM. You can expect that you are dealing with a .NET assembly (and COM is something quite outdated compared to CLR). Try this: add a reference to your project using the tab "Browse" of Visual Studio "Add Refererence" window. (If you are using something except Visual Studio, there is a similar way to add a reference to an assembly by its main module file.) Also, the assembly could be installed to GAC.
But I would advice the ultimate way of using the product: through its source code. The product is open-source.
—SA