Set up your ladder so that it is safe to climb.
Pop the cover off the light that needs a replacement bulb, by simply squeezing the top and bottom of the light cover. There are tabs in the RV light cover that hold it in place.
Unscrew the existing bulb, and put in the new one.
Replace the protective cover after wiping it free of dust and dirt.
Look at how the fixture is assembled. You may need to unscrew the cover of the light to get it off to access the light bulb.
Remove the bad bulb, and replace it with a new one once you have the light cover off.
Clean the light's cover, and replace.