summon anything you can to help, it will distract the dragon
use any high power scrolls you may have found (including conjuration and destruction)
use any resist frost potions you might have come across.
if you have any yet, make sure to remember to use your shouts, they can help too.
if you don't have one, get a companion/follower to help you, most are pretty beastly - you can usually hire one in the nearest town's pub/inn.