Looking at the example code on the library page, you would need to specify the pins in the declaration of the display object:
I2CPreInit gI2C(p9,p10);
Adafruit_SSD1306_I2c gOled2(gI2C,p27);
It looks like the driver also wants a reset pin (p27 in the example code). You can probably just set that to any unused IO pin on your processor since it looks like that display has an automatic reset.