There is probably an official way to do this but this is how I dit it.
Look inside the four corners of the vent about .5" to .75". You should see a small metal tangs with a slot on the middle. The tangs need to be lifted and the vent worked out of the dash. Moderate to medium force should be sufficient. Once out the bulb replacement is obvious. I bought bulbs from the dealer for about 2 bucks each but I'm sure the local parts store has them too.