UV mapping is defining co-ordinates on your model to map the textures too, if you are completely new to it all I would look at one of the many tutorials on youtube.
Start with learning to make a mesh (the 3d shape in space)
You can then get your basic mesh in to RoR to play about with.
Next learn UV mapping (applying a texture to the 3d shape) and Texture baking (to bake ambient occlusion to your textures)
That will let you get your mesh looking a bit better in RoR.
Break it down in to manageable steps.