I fear you're on a far too complicated path!
your link about the Evaluation Board - ADXL345 says
" The UART pins are also broken out allowing a direct TTL interface with the processor. "
You just need two digital pins and GND from the Arduino and connect that directly to the ADXL uart. (Rx to Tx , Tx to Rx, GND to GND)
Then look for the Arduino SoftwareSerial Library, and hopefully you see it's all done, already.
The next task is you probably need to see on the PC what's going on,
so you might like to copy the communication (both sides) to the standard serial.println to log it in the PC Arduino Serial Monitor.
thanks for your advise. now honestly i have no exact idea on it. I try connect it with TX (from eval adxl board)to RX on arduino...i did print it on serial monitor but it seem llike displayed current value instead of the data i want....i am stuck on it now..