Adding Layers

Excuse my ignorance, but I just started using PS7 a few days ago and can't figure out how to work the layers option. I've read all sorts of tutorials, but I stilll can't figure out the most basic of things. I'm sure the answer is simple but I just can't get it to work and it's frustrating.

I understand what layering is, but I can't add layers. I can make a dublicate layer out of the background, but when I add a new layer it is always the same checkboard sheet. I can't figure out how to change it, how to add layers made from other images. Every time I access another image to get another layer, my previous layer of the previous image has always disappeared from my layers palette. I've tried locking them, I've tried organizing them by putting them in sets, I've tried many different options but I just cannot get 2 layers of 2 different images on at the same time in my layers palette., so I can link them and merge them. What am I doing wrong ?

Thanks for any help.

Try Googling on photoshop layers - I did and found lots of tutorial links including these two......


PhotoShop Layers 101



Collaging - Merging 2 images with a layer mask.