You'll need to get to grips with the Layer shader. This creates a stack system where you can use images, effects and shaders to add/multiply/subtract and mask other layers. Once you get your head round it, it's pretty logical. You can apply the Layer shader at any time, and it'll put whatever is in your texture slot into a layer. You then add an image, shader, effect or a folder from the buttons. To edit a layer, click on the small square icon next to its name. Click and a hold that icon to reorder layers. Let us know how you get on!