Place your headphones on a flat surface and away from external audio sources, such as a PA system or stereo. Placing headphones too close to an external audio source can cause "bleed-through" into your audio.
Place your microphone between the left and right cups of the headphones. For best results, put the pickup of your microphone close to the bottom of the headphone cups to allow the headphone audio to be broadcast just in front of the pickup of your microphone.
Enclose your microphone between the left and right cups of the headphone with strong rubber bands or adhesive tape. A tight seal between the left and right cups of the headphones helps prevent "bleed-in" from outside audio sources and brings the speakers of your headphones closer to the microphone.
Turn up the volume of your headphones loud enough for the microphone to pick up the audio. The headphone volume will likely be louder than it would be during "regular" listening, but be careful not to turn the volume up so loud that the audio distorts.