Sensor output goes to an anlog input.
Read the datasheet..: It says ouput is 8mV/g
float a;
void setup()
{
Serial.begin(9600);
}
void loop()
{
a = (analogRead(A0)-511) * 4.8875855 ; //millivolt
// 5/1023=0,0048875855 V/step
a = a / 8; // 8mV/g
// all calc can be done in one calculation
Serial.println(a,2); // G-value
// shoud be 0 when not moving
// expect small values when 'shaking'
}