Have you read the datasheet?
http://www.analog.com/media/en/technica ... 0_5282.pdf
It is an I2C compatible device.
Connect the SCL pin to pin 5 of the Pi
Connect the SDA pin to pin 3 of the Pi
You will also need to connect the AD5280 to 5V and Ground. The ground should be common with the Pi's ground pin.
The second link above also gives you some info about how to test if the device is connected using i2cdetect.