If you still want to do it with an Arduino, you need a voltage divider an an analog input, and use the digital pins for the Leds. Since arduino can only handle voltages from 0 to 5V, you need to divide your input by 3 (more or less). So a voltage divider using a 10K and a 4K7 resistor will do the job.
Just wire Vout to the Analog input and then do the software.