Things You'll Need
Instructions
Start "Half-Life 2" by double-clicking the desktop icon or booting the game from Steam. The game will boot to its main menu.
Click the "Settings" option.
Click the "Controls" tab on the left side of the screen.
Scroll through the list and click in the "Voice Chat" field. A small window will appear. Press any button on your mouse or keyboard that is currently not assigned to another key to set the "Voice chat" button.
Enter any multiplayer match. You can see a full list of available games by clicking the "Multi-Player" tab from the main menu.
Press and hold the assigned "Voice chat" button. Your microphone will be activated as long as you hold the assigned button.