The Arduino analog input is limited to a 5 VDC input. If you wish to measure higher voltages, you will need to resort to another means. One way is to use a voltage divider.
It is fundamentally a 5:1 voltage divider using a 30K and a 7.5K Ohm resistor.
GND – This is where you connect the low side of the voltage you are measuring. Caution! : This is the same electrical point as your Arduino ground.
VCC: The is where you connect the high side of the voltage you are measuring
S: This connects to your Arduino analog input.
– (or minus): This connects to your Arduino ground.
+: This is not connected. It does absolutely nothing.