The resistors wired in series from 10V to Gnd make a voltage divider. You feed the analog signal from the junction into the arduino.
Vin : resistor R1 : Vout at junction : resistor R2 : Gnd.
Vout = (Vin * R2)/(R1 + R2)
Vout = (10V * 5000)/(5000 + 5000) = 5V
Connect all Gnd's together.