Set up your height equation, then factor or use quadratic formula to find when h(t)=0
Step-by-step explanation:
Your equation will be -16t^2+vt +h where v is the initial velocity and h is the starting height. Now either factor or quadratic equation, whichever is easier for you.
Remember that the ball is on the ground when h(t)=0 since that is the height. There will be two zeros, one is a negative number so would be before you kicked the ball, the other one will be when the ball comes back down.