I am not there and don't know what am "looking" at but will take a guess that 12-0-12 means this is a 3 prong power plug, so without further input I guess the two 12s are simply two different rails (I don't know how to explain RAIL but it's a power supply terminology) so you should be able to take the single battery +12 and hook up to BOTH 12.
Now I don't know and you did not disclose whether this is a car amp component which tend to have, besides the main 12 volt supply (switched by ACC on key), another 12v input for "always on" or 12 input is a remote trigger.
Always have a fuse when dealing with car's hi amperage battery.