How to install car audio?

hello i know the basics on how to install amp and a sub but i was wondering about voltage and the car battery how do i upgrage ive heard u can use the small forklift battery is this true if so would i have to charge that please help ps the amp i want to run is an Orion HCCA-D5000 MONOBLOCK CAR AMPLIFIER 2500W RMS its for a sub