Before we begin, let's start with a brief rundown of your most used panels in Photoshop. I'm running Photoshop CS6 so if you have a different version it might be a little different, but they are overall the same. Here is the general layout:
The tools panels holds all of your weapons. It includes your selection tools, brushes, pens, shape tool, gradients, dodging and burning, healing tools, color selections, eraser, etc. You will grasp the fundamentals of using some of these tools and apply them into our poster.
The color panel is the use for selecting colors. You can change colors of objects by using the sliders and changing the Red, Green, and Blue channels.
The adjustments panel is for creating adjustments such as brightness, levels, exposure, color filters. You will apply different adjustments to create different effects to our images.
Our layers panel organizers each of our layers that hold certain elements we use. If we imported several images, each would have it's own layer. Move layers around to tile items on top of each.