Turning relay on by ignition wire?

I am trying to put a laptop in my car. I already bough a 12v adapter for car. I am trying to hardwire to my car using a realy. I want the charger to come on when the ignition is on. How would i wire it the relay??

Hook up the charger where the Lights are on this diagram.

You don't really need a relay, just a fused wire on the (+) wire of the car charger running to a switch ignition wire off the ignition harness. Ground the (-) wire to the chassis and your good to go. The relay won't really help anything.

85 is iginition wire, 30 is power wire straight from battery(+),86 is ground and 87 is (+) to laptop charger right???

HOw many amps does the 85 put out for the relay to kick on???

85 is just used as switch right???

Oh forgot to also ask.. I am also going to install whelen strobe power supply to run strobes in my car..

And i wan to run relay  for it too because it draws alot of amps. Would i wire it the same way as above digram?? I wan to have a switch for it tho.

After i hook it up can i check it with mulitmeter to see how much it is drawing?

Fuse the hot lead for the amps that you will draw.

yes same way.