I can have an image open in the editor and either copy another that is in the editor or from an outside source and paste it in that document. What is not working? Can you provide some steps so we can narrow down what is failing for you?
When you say "set" it, do you mean you flattened it? If so then you have merged all the objects on the canvas into one. If you use undo to the point where the flattening occurred, you can then move the object.
If that is not what you mean, please could you elaborate?