There's a couple threads on installing these, but I figured I would post up my install pics to give another view of installing these on a 2012 JK.
The kit from PIAA ( PIAA 85110 115db 400HZ + 500HZ Sports Horn ) includes two horns and leads for a single horn. I split included leads and added blade connectors so they could be plugged into the stock wiring harness without cutting or splicing the factory harness. I soldered everything so I know the connections are good. Once that was all put together and stock horn removed, I simply bolted the two horns to the mounting hole for the open hood sensor (I don't have remote start so I don't have the sensor). The second horn sits up high, but the hood can close without an issue.
They sound about as loud as the stock horn, but are far deeper and better suited to a Jeep. Not a bad upgrade for around $40.
Hope this helps!