querying in FOWL

Hello,

I am using the FOWL inference engine for my OWL ontologies. Does anybody know how to query the knowledge base for all instances of a particular class?
For example, if I create the class File in my ontology. I load the ontology in the KB, then I create an instance document with instances of File and load it in the KB. How can I write a query to get all instances of File?

Thanks,
Prajakta