In the inspector is a section titled "scene" and in it you will see all the nodes with your character and other images in. If you pick these up and drag them you can change the order they are created so that a node will show on the 'top' or 'bottom' as you wish. If you pick up your character node and drag it to the bottom it will show above the other nodes.
Just so you know there are also nodes such as Y_sort which can draw them in order based on where they are on a y axis.