With white you start at the top and make a line with a little bow. (if i'm saying it right) than a right line down and bring the two line together with a bow again
than you kind of split (starting in the middle) the two lines to the bottem of the nail.
Now you fill in the butterfly with white
when the nail is dry enough you take a fancy color and fill in the butterfly half and give the butterfly a body with green. you only have to make a line from the bottem to the top of the butterfly
Now with another fancy color (like blue) you fill in the rest of the butterfly so you almost can't see any white.
with black you follow the contours of the butterfly and you fill in a little bit.
make a line from the place you fill in with black to middle of the body (you don't have to if you can't make fine little lines like I can't =P it's just what you like) take the green of the body again and make line from the body to the top of the nail with a little bow again.