Okay, so we’ve found our frequencies. The first reaction here is to try h = e, and since we know the cipher used is the Caesar cipher we can try a shift of -3 and viola, the message is revealed. But what if we didn’t know the cipher – could we still figure this out, assuming the cipher didn’t mask the frequencies? Well with a little clever thinking, of course!
We can make the assumption that h is going to be the letter e here – it’s the most frequent. So already we can narrow some things down. We can take a look at some of the words and make further by looking for short two to three letter words and trying possibilities – there are only a handful in the english language. We can also look for instances of repeated letters as only a few letters repeat in such a fashion in common language). From there, it’s a matter of determining from words that you think you’ve figured out and using their letters to crack more words, eventually revealing the entire message!