i've been looking it up and asking around. basiclly the answer i got is ground to the chasis (as close to inverter as possible) and for the +12V go to radioshack and get a blade fuse tap. since civics generally have lots of empty fuse spots in the box, i'm assuming that u do also. if you search the power supply forum for "blade fuse tap" u will find lots of info. sorry my thinking is kinda disjointed. i'm exhausted. so back to what i was saying- by connecting the + to the acc fuse box (with a fuse in-line) the inverter will only get power when the car is running or key is at acc position.
i'm going to put a switch on a relay in-line with the + wire because i tend to run my radio while my car is off.
good luck. hope this helped.
oh. also forgot to mention. if you get the tap that is only a single blade then make sure u plug it into the correct slot (i.e. use a multimeter)