First off, the eyedropper tool is a colour selector. I use that alot when blending images, and trying to keep the same colour. Lets say for example, I wanted to make a Toronto maple leafs signature with my name on it, and my name to be the exact colour of the maple leaf. Just use the eye dropper, and bam! You have the exact colour.
As for backgrounds, are you just inserting a picture or wanting to make one?
If your just puting a picture for the background, simply make it the first layer. Then all the other layers will go over top. The layers work like cutting and pasting pictures onto a peice of paper really.
That helps a little,but you know the swatches palette and the styles pallete to the right, how do i get them onto my sig.