This is what the chatbox looks like. To open this up just press your Arma 3 keybind for using the chat system. Type in any Message or command and it will be send out to everbody. Your name will be displayed.
| Different Chat WIndows
|| Click here to open the settings off the chat system.
|| In the Lobby the "normal" chat will be displayed. Like whenever something is written by another player in chat it will be displayed here.
|| In the Private Area all private messages will be displayed.
|| All system messages will be displayed here. For example when somebody connects, all server save messages, vehicle storage messages and so on.
type in !help in the chat to see the image above
If you type in "@" in the chat, all online players will be shown and you can select one of them and send them a private message only they will see.
After pressing your chat key (arma default) click with your mouse on the settings button on the top left of the chat box. The windows as shown above will be displayed. You can change the colour and the font of the different chat systems.