It's a bit more complicated. Go to https://github.com/TCoS-Rebirth/TCoSReborn download the project, download Unity, open the project in Unity and either build the server or play it inside the editor. You can then connect to this instance (you may have to set up your configuration first if you start it from a build, this thread also has some more information: https://www.spellborn.org/thread-292-page-2.html)
Edit: i'm trying to upload prebuilt binaries to the release section on github, but those are without the readme, you have to get that from the other thread
(Edit2: here: https://github.com/TCoS-Rebirth/TCoSRebo...perimental)