I am currently doing this project, that needs to store the X,Y,Z values from my fall detector, ADXL345 to the sd card shield and then it will directly export out to an excel graph. However, I am still stuck in storing the results to the sd card.
If this is class project you need to learn by doing. There are many examples of what you need in this forum and on the web.
If this is not a class project specify you requirements. What is your hardware setup? What sample rate is required and how long is the sample period? Any other requirements?