$ sudo apt-get update
$ sudo apt-get install fusionforge-plugin-gravatar 

fusionforge-plugin-gravatar is installed in your system.

Make ensure the fusionforge-plugin-gravatar package were installed using the commands given below,

$ sudo dpkg-query -l | grep fusionforge-plugin-gravatar *

You will get with fusionforge-plugin-gravatar package name, version, architecture and description in a table

fusionforge-plugin-gravatar package basic information: