oh to merge layers if u have the layers tool bar up (if u have only one layer u want the text on and have like 6-7 layers) then you make sure the eye is only on the images u want merged. Then go to Image and the 6th thing from the bottom says merge visible layers (aka anything with the eye on on the Layers tool bar will merge) ^^
if its just a simple bg with some text or an item on it you dont need to worry about looking at the layers tool bar at all.
Also if its just some picture you are putting on a bg a simple click with the wand tool on the bg will ancor (aka merge) it.