Cannot seem to use TFS API, how to correctly import items from the SDK?

问题

I am trying to write some simple code to connect to a TfsTeamProjectCollection, however, I continue to get the message :

"type or namespace name 'WorkItemStore'/'WorkItemCollection'/'TfsTeamProjectCollection'/'Project' could not be found."

I have tried to find the TFS SDK, and how to install it, but I can't seem to figure this out - I seem to be blind as this is definitely well documented somewhere. I believe I need to install some of these items, and then add them as references to my project? Could this be correct ? Which of these items do I need ?

Thanks very much, apologies for the silly question - I have recently given up coffee!