Press the green flag to start, and the space key to reset. It will ask you what number you would like to factorial, factorial means the number times itself minus 1 then minus 2 and so on until it's times 1, so for example, 5! ("!" means "factorial", so 5! is 5 factorial) is 5x4x3x2x1=120. So anyway, after it asks you what number you would like to factorial, type in your number and it will give you the answer. If it says "Only use whole numbers!" then that means you did not use a whole number, factorial only works with whole numbers. The whole numbers are {0,1,2,3,4,5,6…}. Oh and also 0! is defined as 1
