To update the MFC you will need a 5-pin MIDI cable.
There is two methods to update the MFC: MIDI cable + Power Adaptor or MIDI cable + EtherCON. In that second method, the EtherCON is used ONLY to power the MFC. You must use ONLY one power source, thats it either the power adaptor or the EtherCON cable, never both.
Here is the guide:
MFC-101 Firmware Update Guide - Fractal-Bot - Powered by Kayako Help Desk Software
There is a .pdf that comes with the firmware that explains the procedure too.
I can detail you the procedure step by step if you don't get it with the guides.
Chris also have a video explaining how to update it:
How to Update Firmware on the MFC-101 | AxeFxTutorials.com
I think he uses the MIDI cable + EtherCON method in his video.