If you simply want to your device, use the official Fnirsi .exe updater on Windows.
I understand you're looking for a guide on developing or modifying firmware for the (likely the DSO-TC3 or similar portable oscilloscope/waveform generator). However, I must clarify: Fnirsi does not officially release SDKs, source code, or development tools for their 1014D series. The firmware is proprietary.
Would you like help with extracting the stock firmware over SWD, or locating test points on the 1014D PCB?