PS: Need selection tool help

Ok folks, I have a class project where I have to add a butterfly, tree trunk, elephant and rainbow.. I have been able to add everything but the rainbow. It's been giving me trouble, can someone do it and show the actions, so I can see how you did it, and learn from it. The problem is there are really no edges.

Here's the Image in which everything needs to be put into.

IMAGE LINK: http://www.flickr.com/​photos/settntrenz/8841​773781/

IMAGE LINK: http://www.flickr.com/​photos/settntrenz/8842​432214/

The rainbow file is too small, & when I try to get to a bigger file I get, "This photo is private.
Oops! You don't have permission to view this photo."

What class is this? First, I'd flip the rainbow image horizontally, then use a combination of the Soft Light blend Mode and the Blend-If sliders to blend the rainbow into the first photo. I doubt that this class is teaching such techniques though so you're probably looking for something more basic.

Also, I can't help but notice that none of the objects in the composite are to scale; the butterfly is about 1/4 size the man in the foreground, the elephant is nearly the size of the human, etc.

Thanks Folks, I'll keep at it... It a beginners basic introductory class in PS at college. Next course is advanced.

Here is a edited version with elephant and butterfly more to scale

IMAGE LINK: http://www.flickr.com/​photos/settntrenz/8848​829366/

layer mask with the rainbow?