Why is my horn going off by itself?

If you connect the battery and your horn starts going off by itself, it’s indicating something. If it goes off repeatedly, it is indicating an error code. Count the number of times it goes off, and check the bottom of the troubleshooting article for more details.

What is the button/switch on my throttle for?

The button or switch on your throttle leads to two unterminated wires that can be used for any purpose, including reverse functionality and lights. Take a look at the installation article for more details.