I know nothing about nodes, so I tried to use them. I UV-ed my monkey head, and then I colored on it. I brought the image back into Blender, added a new material, then went to the node editor and opened the image. The image shows the two original nodes that were there. How do I set it up and get the image on to the monkey?
You are in the Compositing node view right now which is for post-processing. You need to switch to Material nodes to edit your object's material. To switch to material nodes click on the material icon at the bottom of the node editor.
Now you can add your texture with an Image Texture node and plug it into whatever shader[s] you are using.