I have connected 5 servos to my Arduino. I know I need and external power supply but am not sure how much. When a servo says 4.5-6v is that per servo? How many total volts do I need and what batteries would be the best choice?
No, you need a 4.5V-6V (let's call it 5V) supply, which can supply enough current to supply the sum of all the currents your servos will require, which will be connected in parallel. If each servo requires 500mA, and you have 5, and they can all run at once, then you need a supply capable of \$500mA * 5 = 2.5A\$, plus enough to run whatever other devices you have in the circuit, plus maybe 20% margin for robustness.