1999 Ford F-150 LIGHTS FLICKERING

MY TRUCKS LIGHTS, HEADLIGHTS, TAILLIGHTS, INTERIOR LIGHTS, AND DASH LIGHTS KINDA FLICKER. THEY DON'T GO ON AND OFF. IT REMINDS ME OF LIKE A PULSATING. I HAVE BEEN TOLD BY A COUPLE PEOPLE THAT IT'S A GROUND. IS THIS TRUE? AND WHERE DO I BEGIN? I'M NOT GOOD WITH MECHANICAL STUFF BUT I DON'T HAVE THE MONEY TO TAKE IT TO THE SHOP EITHER. THANK YOU FOR YOUR TIME AND HELP.