VIN and GND are power in pins, you can use 3-5VDC so its great for any kind of microcontrollers. There's an on-board 3V regulator as well, the output is available on the 3Vo pin (you can snag up to 150mA)
For I2C, connect to the SCK (i2c clock a.k.a SCL) and SDA (i2c data) pins. These are 5V safe so you can use them with 3V or 5V logic
If you want to use SPI instead, you'll be using the SCK, MOSI, MISO and CS pins
The AD pin is used to select SPI or I2C interface, and if I2C what address to use. See the wiring page for more details
The IRQ pin goes low when a pin is touched. We don't use it on our code examples, but if you want to have an interrupt pin used, connect it to this IRQ pin and use active-low triggering.
The RST pin is used to reset the chip, either in I2C or SPI mode. It's optional but using it will make the system more reliable so we suggest it.