I have a background layer in photoshop and I would like to add a few more images on this background. How do I do this? I have set my background layer to layer 0, but I don´t know if that is right or what to do further. I am new to this so I would really appreciate some step by step explanation?
Generally you don't need to modify a layer to add something to it. You create a new layer (push new layer button in layers window) and then add what you want to that new layer (after you select that new layer as the active layer). That way you didn't destroy the original contents and you can alway turn on and off layers that you don't want (using the eye visibility). If you want to modify content on a layer you can duplicate that layer and then modify it, preserving a copy of the original.
Adjustment layers and masks are also great ways to make non-destructive modifications to layers.
I have now made a new layer, but I still can´t import/add another image to this new layer? Can I do that or did I misunderstand you? my images are on my desktop, I seems like I can only import one image at the time or it only changes out my previous image with the new one?