at the very least, you should tell us by what you want to replace these words. Also, these words you want to replace, are you supposed to hard code them in the program or are they coming from another source (e.g. a file).

Finally, this seems to be a homework assignment. Please tell us upfront if this is the case. It doesn't mean that we are not willing to help, but we might insist more on seeing your attempts, to help you correct your mistakes.