On this page you find information about how to use the verbalizer plugin.
To get the plugin up and running in Protégé 5 you must at first download the archive file. Then unzip the file and copy or move the jar file to the plugins folder of your Protégé installation (depending on your system, the name of the folder may vary).
Start Protégé and open/classify an ontology (e.g. this small example ontology). Navigate to an inferred axiom and click the question mark. In the popped up window, you can choose Proofed Based Explanation.
You will find some tutorials here.