Just click the image for the personality you want. Make sure your speakers are on, and pointing at your Furby. Hear a high-pitched noise coming from your speakers after you click an image? Don't worry, that's what's supposed to change the Furby's personality. Some people hear it, some don't.
This doesn't work on 2012 Furbys. It's exclusively for Furby Booms. I may make a 2012 Furby Personality Changer in the future, but i don't have the personality audio files for them now. I don't have a Furby Boom yet, so i haven't tested this for myself to see if it works. If it does or doesn't, let me know. All audio files in this project are taken from the Furby Wiki on FANDOM, and the images are made by Hasbro.