there are typically two steps required before you can use classes from some managed DLL:
1. add a reference to your project; in Visual Studio, right-click your project, choose Add Reference,
wait a while, locate the assembly file of interest, and go.
2. in each source file going to refer the classes of that assembly, add a "using someNamespace;" statement for your convenience. (The odd programmer will tell you you could skip that and always use fully qualified class names).