Once I've read an ontology, how do I visualize an OWL file in RDFScape ?
Once you have read an ontology, this is available for querying. There are four query methods: SPARQL, RDQL, Classes and string based. Note that 'Classes' depends on the reasoner adopted and may not always be available (OWL classes). Once a query is performed, a set of results is shown below the query panel in a table. To visualize these results, select some row in this table and select "plot values". Note that only Resources will be plotted (no properties or literals). Now you can right click on a node and expand the network. More complex visualizations are achieved through the definition of visual queries or patterns.
How can I visualize an ontology with classes as nodes and properties as links between the m?
You need to define a pattern that capture the RDF construct for a property, with generic domain and range. If interested pleas email the author. Configuration files for RDFScape for specific tasks will be developed and release depending on feedback.