As you assemble and tweak your initial key- frame you may need to adjust the z-order of your Sprites.  (the order in which they are drawn on screen..in other words, which are in front and which are behind). This can be done by clicking and dragging on the sprites in the z-order palette on the upper-left of your screen or by selecting a sprite on the canvas and then holding Cntrl and pressing the up or down arrows.  You can also hold Cntrl and press the left or right arrows to send the selected sprite to the absolute top or bottom of the z-order respectively.
Adjusting the Z Order of Sprites