You have opened the Relationship Properties window.
Notice that the double-click action in PowerDesigner is polymorphic - each object responds with its own type of proerties window. You don't need to learn a different command to edit each type of graphic object.
With only one or two trivial exceptions (e.g., a free-form line), if you can see it, you can double-click it to work with that object's properties.
We will examine this window section by section.