You can do an anonymous login for running servers separate from your regular user account. Using the steamcmd tool you can install it with something like "steamcmd +login anonymous +force_install_dir yourinstalldirectoryhere +app_update 896660 +quit" then run it. I think it includes a little pdf manual for running the server. I run it on Linux so can't help much more than that though. Read here for steamcmd info https://developer.valvesoftware.com/wiki/SteamCMD

Edit: I guess I never tried running it on the same machine while playing the regular game so I don't know how that would work out.