If you click "How to Play", on the second slide there is an explanation. I've copied it here. Not so easy to follow if you don't know ppt and if you are going to play the game, maybe just skip those slides or delete them.....
First delete all boxes in the desired slide, but don’t delete the slide itself.
Then copy everything from the hangman slide to that one by left clicking and selecting all the items then pressing Ctrl + C.
Go to the slide you want to add it to add press Ctrl + V.
Now just copy the letter and the little box below it at the same time as many times as you need to spell whatever word you want.
Just change the letter to the one you need.
To reveal the letter just click on the little box below it.
To add a part to the hangman for a wrong letter just click on the base of the hangman pole.
Keep going till the head appears or they spell the word.
There should also be sound effects for right and wrong answers.