Slide the scroll bar along until the frequency chart for this portion of the ciphertext shows a good match with the average frequencies in normal English. Then click on the next letter of the keyword to analyse another portion of text.
Babbage defined a series of steps to crack the Vigenère Cipher. Let us try to decipher the ciphertext on the right. We know that it is enciphered using the Vigenère Cipher, but we know nothing about the original message or the keyword. The first step is to search for sequences of letters that appear more than once in the ciphertext. The most likely reason for such repetitions is that the same sequence of letters in the plaintext has been enciphered using the same part of the keyword. You can print the ciphertext and search for repetitions by hand or click "Find Repeated Sequences". The repeated sequences may take a moment or two to appear.