You'll need the FPRO software that should have been included on your KPG-95 software disk.
1. Connect your radio to the PC.
2. Open FPRO
3. Put the radio into firmware programming mode by turning the radio off. Press and hold the bottom side button and the PTT button while turning the radio on.
4. Using FPRO, find the new .hex file, will look like: TK-5410K_FIRM_SH01_REL20.HEX
5. Select the COM port your radio is connected to
6. Make sure baud rate is set to match your radio. 115,200bps is standard.
7. Click "Write".
It'll take a few minutes. It'll show scary sounding things like "Flash Erasing", "Firmware writing", etc. When it's completed, make sure the display shows the check sum that matches the firmware.
Latest firmware for the TK-5210 V3 radio is G6.02.00 Checksum C61E