YOU NEED AT LEAST TWO PEOPLE IN ORDER TO CHOOSE A CHAPTER.

Chapters are sub-divided by game: Ground level Opposing Force, first storey Half-Life + Uplink, Outside area Blue Shift.

If an Area is not accessible, either the server admin disabled it, or the Single Player Campaign is not available on the Server.

Each table with two consoles represents a chapter. You need to press both buttons on a table at once WHILE STAYING DIRECTLY IN FRONT OF THE CONSOLE.
When you fail to open a Portal, you will hear "Access Denied".

For more Information, read the read me.