Seiken Densetsu 3/Part 11: Forcena, Finally

Now you're in Forcena. Go to the castle and speak to the king and he will give you the flute to summon Bookasboo. Go back out, take a cannon to Maia, and get back on the Golden Path. In the first or so screen, go down and reach the beach. Use the Pihyara Flute.

Now you will be hitch a ride on Bookasboo. Head North to the ice continent of Altena, and look for a beach to land on (in a bay). You will enter Snow City Elrand. Head to the lower right-hand corner to enter the Sub-Zero Snowfield.