The guy in the video starts out explaining that, over time, his guitar has started to sound a little funny. He thought maybe it was a cord or wire shorting out, but it turned out to be the battery. He shows us how to change that battery. You are going to need a Philips head screwdriver and a new nine volt battery. Take off the tremolo plate on the back of the guitar. You'll be able to see the old battery in the body. Gently remove the old battery and replace it with the new. Slide the new battery back into the body of the instrument and put the tremolo plate back on. He also states that if you play a lot, you may need to change the battery more often.