I think you need to be a little more specific about that. What exactly is the problem? Where do you get stuck?
Two ideas/questions from the top of my head:
1. Did you work your way through the getting started tutorials here in the tutorials sections? That covers a lot!
2. Write a game design document: What is the gameplay like? How do the gamemechanics work? etc. Then, starting with that you can begin coding/building step by step. If you get stuck, you can ask more specific questions here! ;o)