You must first place another image from Image > Place or drag from another document, then click on layer with image (layer with image which you want behind) on LAYERS palette and drag it below layer with image to be above.
PHOTOSHOP
Photoshop is picture editor,what you mean?good picture editor?best free picture editors are GIMP and Picasa,i recommend to you Picasa
from filter menu
no
Adobe Photoshop CS5
You can use photoshop or another picture editing program to digitally edit the picture.
Adobe Photoshop CS5
Photoshop can do this
Open Photoshop, open your picture in Photoshop from File>Open, then start making changes. Of course if you are unfamiliar with Photoshop, you may want to learn the basics first.
photoshop
A Bitmap is a file you can save pictures as like JPEG or PNG, in photoshop it means save the picture as a bitmap
Photoshop is one such tool for that. Pixlr is another tool which can be used like Photoshop.