There is no one official way. In Skyrim the pronounciation can be different.
Source 1. Speech in skyrim, can be found on youtube.
Source 2. Skyrim theme song, can be found on youtube.

Alternative options. These options are heavily based on peoples options.
Option 1. Learn->memrise course. Keep in mind that the pronounciation there is one person's opinion and might not be what everyone uses. It can even differ from most dragons in Skyrim.
Option 2. Talk with people in the community. After studying source 1 and source 2.