When objects on a slide are stacked on top of each other, it can be difficult to select individual objects. For example, you might want to select one object to apply a custom effect, but it is buried under other items. Use the Selection and Visibility task pane to select that object.
To open the Selection and Visibility pane, on the Home tab, in the Editing group, click Select, and then click Selection Pane.
In the Selection and Visibility pane, under Shapes on this Slide, click the component that you want.In this example, we can easily select the Oval 4 shape from within the Selection and Visibility task pane, whereas on the slide, Oval 4 is buried under the sun, triangle, and connector shapes.
After you have selected the object, you can apply PowerPoint commands and features to that object as usual.