You cannot use Baofeng CPS anymore. Download and install the OpenGD77 Codeplug Programmer. This software is vastly superior to the stock Baofeng CPS.
Run the loader. It will detect your radio in DFU mode. Select the OpenGD77 firmware file (for the DM1702, not the GD-77). Click "Write to Flash." The loader will first erase the stock firmware, then write the new one. baofeng dm1702 firmware update
Open the "Baofeng Firmware Upgrade Tool." Select the correct COM port (check Windows Device Manager under "Ports"). You cannot use Baofeng CPS anymore
Click "Open File" and select your downloaded .bin firmware file. Click "Upgrade." The progress bar will move from 0% to 100%. Do not touch the cable or the radio. This takes 2-3 minutes. baofeng dm1702 firmware update