You can locate the Autumwatch Tower west of Riften and south of Windhelm:
Killing the Dragon
Autumwatch Tower is only guarded by a dragon. You have the opportunity to retreat into a tower in which the dragon can’t attack you with it’s magical or physical attacks. . If you are playing on a higher difficult the easiest way to take the dragon out is by using a bow and arrow. When the dragon uses it’s breath to damage you, retreat into the tower until it stops. Then come back out and shoot it with your bow.
Alternatively you can tank the damage. That is what I like to do because I am a little bit impatient. I generally don’t use a bow and arrow, I wait for the dragon to land and then flank it so that it can’t hit me with fire/frost breath. It will still damage you by stomping the ground, but that damage is significantly less than when it breathes fire or frost.
Full YouTube Walk Through Video
Below is a YouTube video in which I complete this word of power quest fully. I show you my preferred way to kill the dragon and talk about some tactics involved with that strategy.