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.
Once you have it wired up you will need to upload the following code to your Seeeduino. Once it is uploaded and you have some fluid flowing through the Water Flow Sensor, you can open the serial monitor and it will display the flow rate, refreshing every second.