Before you can do any of those things, first you need something interesting to be rendered. You currently have a single go-kart being rendered, which is all well and good, but it doesn't give you much opportunity to see anything if you render a scene into your texture. To change this situation, first you should set up your code to create and render multiple go-karts.
Find the declaration to your go-kart variables for the mesh and textures and replace them with these:
// Kart mesh private const int NumberKarts = 5; private Mesh kartMeshes = null; private Texture kartTextures = null; // Track mesh private Mesh trackMesh = null; private Texture trackTextures = null;
Along with creating an array of ...