In PixPublisher, you have the option of getting additional information on any of the objects you add to your project. You can see this using the Properties Panel. In order to open this panel, click on the VIEW option on the blue bar above the editor. On the pull-down menu, select the option marked PROPERTIES.
Once the properties panel is open, it will show you a number of the settings for that object.
The options displayed will be contextual to that object. i.e. different properties are shown for a Photo as opposed to a Sticker. For example, shown below is the properties panel for a photo. Notice how it has the original size of the photo in pixels - that information wouldn't be available for a sticker or a background.
The X, Y, WIDTH, HEIGHT and ROTATION values can be changed by clicking in the input box and entering a new value, or by clicking on the arrows beside the appropriate input box.