Current firmware on V2.5 / 2.6:
Can update over WIFI. Follow the manual instruction. 
https://www.musicalparadise.ca/files/MP-DX-Manual.pdf

Other versions:
1. Open the top cover. 
2. Use a USB cable to connect between the front screen board USB port and a Windows PC.
3. Turn on MP-DX power.
4. Run ESP-Flasher.exe, select the right com port and MP-DX-V2.6.bin file. Click on Flash ESP.
https://www.musicalparadise.ca/files/ESP-Flasher.exe

Changelogs:
1. Change main screen interface to match MP-DX MK2

2. Fix some digital filter bugs. 

3. Fix DPLL bandwidth