Matrix Voice I2C

Hey there,
i just started working on my Matrix Voice project and i’d like to control an external amplifier through the Raspberry Pi’s GPIO I2C pins. As i see in the pinout these pins are not available on the Matrix Voice’s external connector. But the system architecture lists them (or I2C in general) as part of the “programmable GPIOs”. Now i’ve been looking around but couldn’t really find where to start on this. Would be really grateful if anyone could point me the right direction!