Theres two stages to this. First Stage:
Use the goron (forgot name)and roll into the side of him until he has being knocked over. Than with Link, use a Bombchu to aim at his mouth. Repeat this until he has fallen over dead and a bridge appears for link.
Second stage:
This is part is quite similiar to the boss in one of oracle games, if you ever played it, except a few things (I think it was the Oracle of Seasons). The only you need to worry about is his attacks, which is just flame attacks. At one stage he should do a large sucking technique, use a bomb and throw it until his mouth. Repeat this until he is really dead.
Hope that helps.