1st off here is a pic so you can sort of get the idea of what your going to need to do this.
Now you will need 3 colors. I went with Olive drab as my base then Sand and Green for the camo. Now what you do after you get the base color painted is pull apart the sponge and use the insides. Use the inside because the rough texture is what you want to make the pattern with. Now there is no wrong way to do this just keep on with it till you feel that is the look you want. Remember it's like Dry Brushing, you want to take most of the paint off the sponge before you dab it on the figure.
Here is a start to finish on how it should come out. Hope this helps you guys out short and sweet!