They have a + and - cable with gator clips for the battery.Don't forget the bacon!
Forget the gator clips or cig adapters, you need to hardwire it in there. Use at least 10 gauge cable and put a inline fuse 6-8" away from the battery. Personally, I wouldn't mount it under the hood since the electronics aren't sealed. If you mount it inside then you want to make sure it has some air flow.
For charging batteries and using a laptop, you really don't need a large inverter. They have really small ones for Laptops out there. Unless you plan on running a microwave or a gaming PC, I think 800w is probably enough but you'll want to check the RMS and PEAK wattage usage for whatever you're wanting to use with it.