What is the most logical next event?

How to composite images in gimp
Open your images in gimp.
If they are not the same size, be sure that the primary image is larger than the one that will be composited.
Move what you are going to be adding to the scene, a bear in this instance, up so that it is the top layer.
Right click on that layer and select add alpha channel. You are doing this because you need this layer to have transparency capabilities.