Connect your mobile to the PC using one of the following cables compatible with your S65:
Data Cable DCA-500 (serial->serial) / Data Cable USB DCA-510 (USB->serial, use only COM port 1 to 9). Please note that the Data Cable USB DCA-540 (USB->USB) is NOT supported. start the downloaded firmware file (.exe) and follow the instructions
Finalise the update process with the following steps: 1- enter PIN (SIM required) 2- press *#9999# on your keypad 3- press the "send" button and confirm with "yes" 4- turn off your mobile phone and switch it on again