doubts regarding i2c interface of x15 boards

I need to use the i2c interface of the BB X15 board to connect to an external ADC chip. For this purpose i need to connect the i2c_SCL and i2c_SDA lines of the BB x15 with the corresponding lines of the chip.

Now my issue is, i am referring BEAGLEBOARD_X15_REV_B1.pdf and i found i2c4 and i2c5 are available for connecting to external devices.

so i have used i2cdetect command in linux to see the available i2c ports. This command however is returning i2c0 and i2c2. So is it that my i2c4 and 5 are not enabled? if so what is the method to enable these 2 i2c ports.