How to change car battery?

I changed the battery in my car (97 mercury tracer)and when I connect the terminals my car horn continuously blows and wont stop. I dont have any kind of alarm remote(bought car used) and im stuck. I have no idea how to stop it and get my car running again. please help! thanks|||pull wire off horn would be easy and really shouldnt never buy a used car that you have not crank and drove or check for problems so easy to find horn remove wire then crank car|||Some of those cars had a factory alarm system. Try connecting the battery and then using the key lock and unlock the drivers door. This will turn the alarm off it is a factory alarm system.|||are you sure you have the terminals connected to the right diodes? Also, check your fuses...make sure they are all in snug. Did you buy the right voltage? Perhaps you have to much power and your car is getting a power surge, making your horn blow. sorry, it%26#039;s a bit funny :)|||connect alarm after connecting battery|||are you sure i doesn%26#039;t have a factory alarm?did you get the remotes for the doors when you bought the car?unhook the horn for now and if it wont start the you could have a factory alarm and it wont let you start the car with out shutting it off then you will have to call the dealer and get a remote to shut it off.