If you don't think there will be enough room to add the body with your current canvas size, increase the canvas height. Image > Canvas Size
Use the Pick tool to drag a selection completely around the head, enclosing every piece. Right click, select 'Group'. By grouping all pieces of the head together we can move them around as one unit. Move this group to the top of the canvas.
All shapes created for the body will have a black outline with a width of 2 pixels. Both Anti-alias and Vector should be checked for every step in this tutorial.
Draw an oval with Ellipse tool that has black outline and bright green fill. Ellipse for body should be slightly taller than head is tall (see above image for comparison).