the layout is from pre-blender 2.49. every .blend file saves the layout you were using to work on it, meaning this model was made in an older version of blender.
anyways... id probably start off by opening the model in the default layout, meaning you have to start a new instance of blender, file > open, and at the bottom right uncheck load UI

look for this to the very right and add a new material, select the faces you want to use for that material and assign them
material names should be the same name as the texture, so if the texture is red.png, the material name should be 'red'