How do I make a 3D model of DNA (molecules only)?

I need to build a 3D model of DNA using play-doh or candy or whatever and then sketch a three dimensional diagram of the deoxyribonucleic acid (molecules only) (yellow for phosphates, white for deoxyriboses and any other colours for the nitrogen bases) and I'm not quite sure what that means. I've found examples of 2dish drawings...I'm just totally stumped on what I am supposed to do here. Can anyone help me?