Editing

To add a new class (property) click the mouse.  A new property will appear where you put the mouse.

To add a note, just start typing.  The note will appear wherever them mouse is.

Links are made by pressing the mouse in one node, dragging it, and releasing the mouse in another node.  You can link comments to types, types to supertypes.

To make a link a supertype relation, select the link and select UMLMake sup.