HID Accessory Relay Wiring Harness Install

I'm trying to install the Accessory Relay Wiring Harness for the H11 HID headlights from XenonSupply but don't know where to attach the part that goes to the battery (+).

Here's a picture of the wiring harness:
http://www.ijdmtoy.com/webpage/products/xenon/HID-Conversion-Kit/HID-Relay-1.jpg
The battery (+) connects to #1 in the picture.

I've read some posts where people have said this relay wiring harness was unnecessary, so I tried returning it but was too late. I stated to XenonSupply that I have a Prius C and that my battery is under the back seats and received this response:

"it is always recommended to install the Relay Wiring Harness as it will isolate your HID wiring on its own with its own fuse as to protect your vehicles wiring."

"When the battery is located in the back of a vehicle, there is always a positive terminal post under the hood in the front, which you can use to hook your harness up to."

I found the below picture XRinger posted in another area. Is the place in which this white cable is attached the place I'm supposed to attach the (+) of the accessory wiring harness? If so, how would this be done?

Thanks in advance!

 

Also, what would the advantage be of having the Accessory Relay Wiring Harness installed?

Thanks.

 

Thanks John, but the Prius c does not have a jump terminal under the hood. Direct access to the battery compartment under the back seats is required to jump the car.

 

Thanks for the input. I've had my HIDs in for about 5 months now w/o the wiring harness, and there are no perceivable issues. I did blow a fuse a couple of times when I installed some LED parking, license plate and interior lights, but I think this may be a separate issue...maybe.