Follow Xander´s suggestion. You'll lean a lot of useful and interesting stuff.
To get you on the way with your program in NXT-G, first off, you need a place to do the counting: a variable - starting it with a zero value (you can configure that in the variable block config panel) would be a good idea.
Then you need to have a loop that waits for the touch sensor to be bumped (pressed and released) before it will add one (with a math block) to the value of the variable and refresh the screen to show the change.
As you can see, writing down step by step what you want the program to do is half the job done