FOR THAT YOU NEED TO UNDERSTAND WHAT ACTUALLY KINETIC ENERGY IS.
It is a form of energy which is caused due to motion, when the ball is kicked, it is send into motion thus it gains kinetic energy, how come energy came from ? as you have already read this ENERGY MASS CANT BE CREATED OR DESTROYED. In this scenario the energy is being transferred by the football player into the ball which appears as the kinetic energy of the ball... that's how it works
