You will need
Seeeduino / Arduino
Water Flow Sensor
10K resistor
Wiring up the Water Flow Sensor is pretty simple. There are 3 wires: Black, Red, and Yellow.
Black to the Seeeduino's ground pin
Red to Seeeduino's 5v pin
The yellow wire will need to be connected to a 10k pull up resistor.and then to pin 2 on the Seeeduino.
Here is a fritzing diagram I made to show you how to wire it all up.