Motorcycle Repair: Jump start a Nighster, harley davidson nightster, harley davidson

Question
My son in law bought a 2007 Harley Davidson Nightster about a year ago and has ridden it sporadically.  I would say not even 10 times for a couple of hours at the most each time. Don't know the mileage or the maintenance given to it.  All I know is it's kept in the garage of the house.  The last time he rode it was probably 3 months ago because after that he has been unable to start it. When we have tried to start it, it wouldn't turn over.  I just clicks.  We obviously think it is the battery that just needs a jump or charge as it has been sitting idle.  We cannot figure out how to get to the negative on the battery, and are not the most mechanically inclined persons.  Is there any way I can charge or jump the bike without taking it out?  Is the charge even the problem?  Thank you.

Answer
If you are going to have a bike sit like that the best thing to do is use a battery tender on it. That will keep the battery charged while it sits. the tender will charge the battery and then shut off when it fully charged. If you dont keep the battery charged it wont last very long.
Do not jump start the bike, use a charger. When you attach the charger you dont have to connect the neg to the battery. You can connect it to anyplay metal on the motor that is not rubber mounted
Good luck and happy riding
Mike