Total beginner, grid and cubes

Hi, I am wanting to write a puzzle game. I have had some basic experience before, but nothing like this.

I am wanting to place 100 cubes of varying colours in a 10x10 grid.

How do I start? I've so far managed to get a cube on screen, but being able to place them in a grid, and then to keep track of them, well I jsut don't know where to begin.

Thanks for your help!