AD Explorer shows an object's attributes in the right pane when you select the object and in on the Attributes page of an object's Properties dialog.
You can open an attribute's properties dialog by double-clicking on an attribute or by selecting it and choosing Properties from the Edit menu. The properties dialog also let's you jump to the schema object for the attribute type.
To edit an attribute's value, select it and pick from Modify from the Edit or context menus. The menus also include a Delete entry for deleting attributes. Use the New Attribute entry in the Edit menu to define additional attributes for an object. AD Explorer will guide you through the steps for specifying the attribute's type and value.