Adding a new restriction is very easy using the Visual Restriction Editor.
Select the to which the restriction will apply and click Add.
This will bring up the New Restriction wizard. Select a class for the restriction and then a property to which the restriction will apply (i.e. the restriction's owl:onProperty). Note that it is possible to invoke the New Class and New Property wizards from this screen if either is required.
Clicking Finish will create the new restriction and add it to the document. The Restriction and Value fields will remain undefined until they are manually set as described in Modifying an existing Restriction
Returning to the RDF XML Source Editor, the newly created restriction will be highlighted, and edits made in the Source editor will be recognized by the Visual Restriction Editor as well.