How to convert accelerometer data into G with the ADXL345 digital accelerometer
You need to multiply the resulting acceleration measurement with the corresponding scale according to table 1 in the datasheet. The resulting value is the acceleration in mg.
This means if you configure the range as +-4g fullscale you would have the to multiply e.g. the x-axis by ~4.

But I guess it would be easier if you come up with a specific question or problem you're facing during implementation.