Fast travel to visit Arngeir in High Hrothgar. Talk to him and you will learn the last word of Unrelenting Force. You will go through an initiation ritual. Talk to Arngeir after this, then leave and come back to talk to him again. He will apologize and after some talking will tell you that he cannot teach you this shout because he doesn’t know it. He offers to teach you the shout required to climb to the peak so that you may meet with the leader of the Grey Beards. Follow him outside to learn the shout and then use it to part the snow storm blocking your path. Be aware that you will also be attacked on the way up, most likely by Ice Wraiths. Use fire and heal while using the shout to move forward. Once you are at the top, you will meet the leader of the Grey Beards.