title/battery not working

I have a 2008 50cc velocity, i am from Massachusetts, where i was told we don't have to put a license plate on the moped..however, i am only 14 years old, i have a bill of sale from the previous owner, and the manual(don't no what use that is)and i was wondering, do i NEED the title? i was told by police all i have to do is put a sticker on it saying it passed security/safety check...help please?