Guitar out of tune

I was attempting to do a song on my Fender Jaguarillo, and not for the first time I couldn't get the blasted thing in tune. I then read a Fender guide about how to sort a guitar that is out of tune with itself. Seemingly you can adjust the lengths of the strings using a small screwdriver. This came as a relief to me as I assumed that something was horribly wrong. But a screwdriver is a dangerous weapon in my hands so I've decided to delegate the task my local music dealer.