In order to join a multiplayer game, click the "Join Game" text on the title screen. A menu will pop up with a list of games that are currently running.

On the menu, you will see a list of games that are joinable. The game's name (specified by the host of the game) are colour coded to tell you whether you can join a game or not. A green colour means that the game has not started yet, and you are free to join or observe the game. A white colour means that the game has already started, but you are able to observe the game. Otherwise, the name will be red; where you aren't able to join or observe the game.

To join or observe the game, click the respective buttons beside the game's name. You can see the game's current status by looking at the status box (under the Join and Observe buttons.) You can also see how many players and observers are currently in the game. At the left side of the box, you can see the map and game mode the game is currently taking place in. You can then see some of the game's settings at the bottom of the box. In order, it shows the Experience Modifier, Village Gold, and Maximum amount of turns the game can go up to.

If you joined the game, you will be inputed to select what faction and leader you want to choose. For more information about units and factions, look at the Units section of this help guide.