Be specific! Snowhead in Majora's Mask, or Twilight Princess?
In Majora's Mask: Put on the Goron Mask and play the Goron's Lullaby in the area where there is random wind blowing you back from nowhere(If you look with the Lens of Truth you will see a Giant Goron blowing the wind.) This will cause him to fall asleep and allow you to pass.
In Twilight Princess: Go to Kakariko Village and talk to the Zora Prince at the Zora Queen's grave. He will give you the corral earring to use as a fishing hook. Go back to Zora's Domain and Fish near a rock formation that looks like a big rock next to a little rock. You will eventually catch a reekfish. Release and turn into a wolf. If you sniff it you will get the reekfish scent. Go back to Snowhead and turn on your wolf senses. Follow the reekfish scent up the mountain.
In TP it's snowPEAK.