To change a bulb in an outdoor wall lantern, unscrew the two tiny screws at the top of the fixture. Once the screws are taken off, the top of the fixture will come right off.
You can then take the bulb out and replace it with a new bulb. Then you can put the top back on and screw it back into place.
Nuvo provides an assembly and mounting instruction manual on how to install the Nuvo Essex Post Lantern (NUV-62825). While these steps are straightforward, please consult with a licensed electrician to complete the installation.