Since it's clicking, that means the horn button on the wheel is good, and the relay is good too. So.... the horn itself is shot.
It's on the right side front of the car. You will have to lay down on your back and reach up under the bumper to get to it. It's not too hard to do. 10 or 12 mm wrench, I think.

 

ive had my 1990 LX for about 2 years and about a year ago my horn all of the sudden stayed on until i disconnected the battery after an embarrasing ride home turned out that there is foam that seperates the two plates when the the horn is not in use. all i did was cut little strips of foam from an old couch cussion and replaced the old foam