You don't.
" The FQI system is designed in such a way that the lower the fuel quantity in the tank, the more accurate the fuel indication. The FQI system is calibrated on ground during manufacturing and its accuracy will remain the same throughout the operational life of the aircraft."
Probe faults or FQIC will be announced by CFDS follow the troubleshooting, no calibration required as far as I recall. It has been 11 years now however.