Merge Layers Without Jagged Pixels
by John
(Florida)
Q: I stumbled across a tool in Elements 6 the other day and now cannot find it. It is a tool that softens the jagged pixel edge of a layer when you place it on top of the background - EG if you were replacing one head in a group shot the tool would smooth the edges around the new head as you placed it into the background image.
A: It sounds like you are describing
Anti-aliasing.
When you make a selection of an object (like a persons head) in a photograph and move that selection to another place it might have jagged edges.
The best way to prevent that is to have Anti-alias checked in the Options Bar.

This is the Options Bar (located near the top of the Elements window) for the Elliptical Marquee tool. Notice that Anti-alias is checked.
If you don't have Anti-alias checked, the pixels will give a jagged look to the edges of your selection because the pixels are solid squares of color.
What Anti-alias does is partially selects some of the edge pixels so that they aren't solid but have some transparency to them. This helps smooth out the edges.
In the images below the face on the left was selected with the Elliptical Marquee tool with the Anti-alias box unchecked in the Options bar. The one on the right had the Anti-alias box checked. Look at the difference between the two photos along the outside edges and you'll see the one on the right is much smoother.

It's unclear from your question how you brought the new layer into your photo, but whatever process you used look for something that allows you to use anti-alias and it should smooth it out.
Good luck John.
Until next time,
Rick