Illustrator stacks successively drawn objects, beginning with the first object drawn. How objects are stacked determines how they display when they overlap. You can change the stacking order (also called the painting order) of objects in your artwork at any time using either the Layers panel or Object > Arrange commands.
Click the name of the object above which you want to add the new object.
To add the new object to the top of a layer or group, click the layer or group name.