how to install html agility pack and add a reference to the dll on Windows Vista

how to install html agility pack and add a reference to the dll on Windows
Vista

I have downloaded HTML Agility pack, and after extracting I can see that
there are sub folders with name NET 20, NET 40, NET 40 Client, NET 45,
sl3-wp, sl4-windowsphone71, sl5, winrt45.
I have downloaded Microsoft Visual 2010. Sadly, I cannot proceed further(
i.e., I cannot install Html agility pack in Vista and add a reference to
the dll. I am new in the use of HTML Agility pack and I have the code
prepared by my friend to run. Will be much thankful if you could provide
some insights. Thanks