is it to the negitive side of the battery? or frame somewhere>

 

either one will work. You must find a section of the frame with bare metal. If there is none you can use a wire brush to take some off is need be. Battery (-) works to. The ground for the battery is the bike frame itself.

Theoretically the power transfer will be stronger if you do it directly to the battery, this way the electricity has the least amount of obstacles to travel through before returning to the battery.