Hello Varayut,
You didn't provide enough details as to your setup, so I will suggest that you look at the BLE CC2540 Mini Development Kit User's Guide SWRU270.pdf.
Section 4 of the guide outlines how to use BTool and it gives examples how to read and write characteristics of a simpleGATTProfile. You can apply these same procedures to any firmware you may be running on your CC2540 device.
Thanks,