Click the Team button on the menu to open the Team Window. This is where you can monitor your teammates' health and nano energy, or leave the team when the time comes.
Left-click the Accept button to join the team.
F1 through F6 will quickly target yourself (F1) and your teammates (F2-F6). This is useful for performing actions and executing programs that require targeting.
You can chat with your teammates in private, regardless of their location, through the team chat channel.
Clicking the Friends button on the menu will open your Friends Window, where yoy'll find your friends list and all available chat channels. Left-click the team channel to activate it. The channel in red is your current output.
Any chat channel can be shut off, if you do not want to see it. Click the box next to a channel name to toggle it on/off.