When you use a free hand kit, you have to check if it is compatible with your hardware.
Wether Macbooks and recent laptops offer three connectors plugs (2 for the sound exit and 1 for the microphone entry), older laptops delivers two different plugs, splitting entry (microphone) and exit (sound).
In that case, if there's an integrated microphone in your laptop, it will be the main one. You will have to stay close to it. If there's not, you will have to plug a jack microphone, a USB microphone or a USB headset.