How to connect to a Minecraft multiplayer server:
1) Open your Minecraft game.
2) Click on the "Multiplayer button"
3) Click on "Add Server"
4) On "server Address" enter the IP Address of the server (you may need to enter the port too), it can look like an IP Address (numbers) or like an URL (name of the server).
5) Click on "Done", now the server list will contain the server you just added.
6) Double click the server you want to connec to (or select it and click "Join Server").