In the "Properties" Dialog opened via function key F6 for a Class node type from the "UML" palette section, the last tab should be named "UML", not "Shape". Maybe you have accidentally selected the wrong node or have changed the type of your Class node?
Anyway, on the "UML" tab you can specify the names of your class's attributes and methods. To change your Class node back to node type Class (in case you accidentally have changed its type earlier): select it, then right-click the Class node template in the "UML" palette section and choose from the context menu "Apply Type".