Unscrew the lowest adjustment on the main pole of the microphone stand. Unscrew it all the way so that you can fully remove the extender pole in the microphone stand or at least the head or adjustable arm of the microphone stand.
Place the head of your microphone stand in a safe place, where it won't be damaged, lost or stolen. You will now only have the base section of your microphone stand remaining.
Attach the metal music stand attachment to the base part of the microphone stand. This should be able to slide onto this microphone stand pole and tightened down so that it will stay securely in place. If this does not work due to a sizing discrepancy of the microphone stand's pole or the attachment on the stand itself, purchase a music stand attachment which clips onto the microphone stand pole. This allows you to reattach the microphone stand head and effectively use both stands at the same time.