Many times there are already Power Grid games underway. Sometimes you will find one just beginning. Each "room" is represented by a row on this page. Each room has a table depicted on the left side and if there are other gamers present you will see figures either standing directly around the table, or slightly to the right of the table if they are just visting the room.
On all of the Game Manager screens there is a red arrow pointing to the left in the upper left corner of the page. Click once on this button to be taken back to the previous Game Manager screen.
In the upper right corner is a button ("Reload") that, when clicked once, will cause this page to be reloaded/refreshed. Along the right side of the page are two up and down arrows used to scroll through the rooms for this game.
Each room has a title showing the name of the game. If the title begins with an "*" that game has already started. There are also two buttons in each room. "Visit" takes you into an already started game as an observer. "Gameyell" will launch a new game with yourself already joined and post a message inviting other gamers to come join you. If you just click in the open space in the room you will enter the room without joining or launching a game. The "Gameyell" button changes to "Join" if there's already a game forming but not having yet started.
Since we will be launching a new game, I'll just press "Gameyell" in an empty room.