Do you already know how to connect to the hub server? If not, the IP is us.mcgamer.net. If you are in the UK, you can use eu.mcgamer.net.
Once you are there, you can either walk to the Survival Games building, or click on your compass, and then click on the corresponding item for the location you want to go to in the GUI that pops up. Once you're in the building, there will be lots of signs, which are essentially the lobbies. Find a sign that says "Lobby" on it, and click it. This will teleport you to an area where you will wait for the game to begin.