As Aldo said, should be a smaller round button in the center of the rocker switches on the back of your sterling wheel. One side changes between the presets, the other side changes the between the modes AM/FM, SAT, AUX, etc.
Thank you so much, I have had the car over a year and never knew that I just knew I could adjust the volume and scan channels. That middle button makes my life so much easier now. :grinbiginvert::redblob: