If you Google "Arduino 4-wheel robot" you will find many examples such things which have been built. Many of them include code.
If that's not enough try giving us some more information. For a start, what do you want the "4 wheel base" to do? What motors does it use? Do you already have a motor driver? Is it controlled by something (if so what?) or is it autonomous? What will it be powered with? What "arduino card" do you have?
Have you done anything yet? If you already have some code then post it here.
Steve