The horn on this car is pathetic (only one?) so I have a pair of Stebel Magnum Blasters,to install. The connection on the stock one has two pins and wires,is one power and one ground?How do I hook this up through a relay to the new horns?The new horns have 2 connections on each horn.

 

Yes, it is one hot and one ground. You would hook the new horns up in parallel: connect a hot wire from your old connector to the hot terminal in each of the new horns, and a ground wire from the old connector to each of the ground connections of the new horns. It's a good, simple mod.