Good Luck! :)
Step1: You will draw a circle on the green ground
Step2: You will draw another circle across the big one, the second circle has to be smaller than the first one
Step3:You will select the big one
Step4:You will choose the tool named "Follow me" and select the small one
Step5:You will choose the tool named "Eraser" and you will delete the big circle
Step6:And you will have a sphere!!!