For the stream a dedicated CS:GO server is used. During the stream it is used for trainings or viewer games and is therefore available to the public. You can get infos about how you can connect to this server during when participating in the stream or just use the command down there.

If no stream is live and the server is in Deathmatch mode (you can tell that by the server having [DM] in the server name) it can be used freely. The following console command will connect you directly to the server:

connect cs.yorvex.tv