How does a criminal background work?

How do you work with the "background layer" in photoshop?

• Im' working on a photoshop document. I've been given a 2D pdf file and have been asked to fill in material into room. the background layer in locked and white and i cant figure out a way to create the "lines" layer to start working on it. I've tried duplicating the background layer and then creating more layers, but whenever i place a material or color a wall, I cant see the lines anymore. Does any one have any suggestions?

• Answer:

  Photoshop works in layers and you have to think in layers. First off duplicate the background as you did. You should have one background and one copy. From the layers windows ( Windows -> Layers ) you can move the background with the lock into the garbage can. Now you need to add new layers and add your new elements to each layer. Hope this helps.