When you initially run ResEdit, you get a scrolling window similar to the one you get when you choose "Open" from a programs File menu. Click on Example #2 button for an example.
At this point, double-clicking on any of the filenames visible will immediately open that file and list it's resource types; folders will open a new window that lists all the files in that folder (including more folders). Datafiles from programs like MacPaint will come up with a message saying that the file has no resource fork - do you want to add one? I say no (because what fun is a file with no resources) but if you say yes it doesn't seem to bother anything. When you then double-click on a resource type, it then opens a listing of all resources of that type within the file you chose.
DA, File and Edit Menus are in place. Windows that are overlapped are brought to the top by clicking in their visible area. All windows can be relocated (if not resized) to any area of the screen. When you open a new window, it appears just to the lower right of the active window. Remember what I said earlier about Standard User Interface? All this makes for a very flexible working "environment" (as programmers like to say).