Elizabeth, There are a a lot of way to do that. The best way is to use the pen tool and knock out the background ( or select what your saving ). But the pen tool is Tuff to explain and a hard tool to master with out seeing how to use it first hand.
So here is a way thats a little less complicated. It's Done with the Layer Masks.
Cut and paste the two images together.
Set up your layer pallet with the back ground under the image your going the knock out. If the back ground is on top of of your foreground, click & hold a layer and drag it up or down. Click on the layer mask buttom at the bottom. This will give you the box next to the layer 2 icon. Now using the Brush tool and black and white colors you can paint a mask that will block out what you want.
In my example, I set Layer one to multiply. Then erased the background out of the bead. The reason I set it to multiply was to save the shadow. But you can work the layer mask on ether layer. If you make a mistake while painting the mask just switch from black to white and erase the mask.
Ajusting the opacity on layer 2 helped to soften and blend the shadow.
After your happy, you will need to flatten the Layers. To do this, Click & hold on the arrow point at the top right hand corner. This will open a Dialogue box. There you will find the FLATTEN IMAGE command.
I don't know if elements has this tool but check it out.
I hope this helps.
Scott