Tool bars are located on both sides of your image. The one on the left will display all of the tools you may use to retouch an image: paintbrushes, selection tools, text, color wheel, pen, magic wand, cloning tool, paint bucket, cutting, etc.
Just below that are the configuration options for each of those drawing tools. You can adjust the parameters to fit your needs: transparency, color, texture, thickness, anti-aliasing, etc.
The toolbar to the right displays history, layers, and channels, as well as types of paintbrushes, textures, and gradients.