I have Elements 12, i have edited two pictures of my grandchildren from different times. I want to "slide" one picture behine another to giver the effect they atr all together.
I know i can flatten them afterwards to reduce file size.
1.Open picture B, and use one of the selection tools, e.g. selection brush or lasso tool, to select the grandchild. Once the selection is complete, you will see an outline ("marching ants") surrounding the selection.
2. Go to Edit>copy to place the selection on the clipboard
3. Open picture A
4. Go to Edit>paste. The grandchild B will come in on a separate layer.
5. Activate the move tool and position B. You can also resize, if necessary, using the corner handles of the bounding box.
I have done that and i just get picture A covering picture B, i want it to slide behind picyutr A
You can't "slide" something behind something else. My concept of what you are trying to do is to add one grandchild to the other one in the picture, I assume that there is sufficient space to add the other grandchild. If not, you will have to enlarge the canvas.
When working with layers, it cruicial to make the appropriate layer active in the layer's pallete.
If you follow step #1, you will select just the grandchild (B) . Nothing else.
You then copy, and paste onto A. If the the B selection is too large, you can make it smaller using the corner handles by engaging the mouse and pressing towards the center. (The move tool - step #5)
Hope that this helps.
Further to above, for illustration, I selected the little girl from a photo file and positioned her on the lawn next to the barn. Note the layer structure in the layers palette.