Instructions
Plug your microphone into your computer. Consult your microphone's instructions on how to properly set it up, as every microphone is different.
Launch "World of Warcraft."
Click "Options."
Click "Voice," located on the left side of the "Options" menu.
Click the box next to "Enable Microphone," under the section labeled "Talking."
Use the "Microphone Volume" slider to adjust the volume of your microphone.
Select the method that you will use to activate the microphone. "Push-to-Talk" requires that a keyboard key be pressed before your voice is transmitted, while "Voice Activated" will transmit your voice when it is detected.
Click "Okay" and restart your game. Upon restarting, you can use your microphone in-game via the method you selected.