How do you

To get to the dungeon on Snowhead, you need to get the scent of the Reekfish. To do this, go to the entrance of the Snowhead mountains and talk to the woman. She'll give you a sketch of the monster. Show this to a Zora and they'll tell you that Prince Ralis was the only Zora to catch a Reekfish. Head to the graveyard at Kakariko Village and talk to Prince Ralis to get the Coral Earring. You can now catch the red Reekfish and learn it's scent (in wolf form).

After you enter snowpeak you will see a lady standing in front of you speak to her and she will give you the sketch of the beast that's been coming into the domain. After that go to kakariko village and enter the graveyard go to the very back of the graveyard and you will see prince ralis show him the sketch that the lady gave you and he will give you the coral earring alowing you to capture reekfish. The reekfish can be found swimming on the right side of zore's domain. Catch the reekfish and switch to your wolf form and learn the reekfish scent. After this switch to your senses and you will see the trail of the reekfish scent alowing you to be guided threw snow peak.