Hi Loftprojection,
You can connect this wire from the battery's negative terminal to the GND tap on the charger jack.
The charger jack has two terminals. One is positive and it goes to the switch. The other is a GND and you can connect teh battery's negative terminal to this point.
Regarding removing the battery, it is best to remove the right side panel and top cover. Then use a wide flat-head screwdriver to pry the battery from the VHB adhesive tape.
Hope this helps,
Vinnie
PS: If you still need help, email me and we'll work it out.