The way to get into custom servers on Minecraft is to Open it up, click Multiplayer, and then add server and add one or as many as you like of the servers and try to get on. A better way to do it is below.
To get into a server choose from one of the many servers:
US Servers:
http://www.minecraftsurvivalgames.com/pages/servers-us/
EU Servers:
http://www.minecraftsurvivalgames.com/pages/servers-eu/
Try to get into a game that is in a Lobby. If the server is full, you cannot join. If you get into a server and it is currently in a game, you have to wait until that game is over. Afterward the game will go into the Lobby for 5 minutes and will begin a new match and then you will be playing. If you die you respawn as a spectator and will have to wait once again until the next match starts.
When the game is in a lobby for 24-man servers there is a minimum of 12 people to begin the match. So if you are in a lobby with only 4 others, the timer will continue to restart and you won't be able to play. If you need anymore help just
pm me or post on the forums in the section below.
There is a TeamSpeak 3 server for the survival games:
ts.mcsg.in
There you can ask for help and get to know the people you are playing with and learn tips and all sorts of goodies!
Happy Survival Games!