This was the solution to my problem. I still need help with step 2 in Matlab regarding key length can you give an example?

First, calculate the Index of Coincidence (IC) for the given ciphertext. If the value of IC is close to 0.065, then the Vigenere cipher has been used.

Use Kerckhoff's method to find the length of the key by calculating the IC for each displacement from 2 to 30. The displacement that produces the highest IC value is likely to be the length of the key.

Once the length of the key is determined, divide the ciphertext into blocks of that length and calculate the frequency distribution of each block.

For each block, compare the frequency distribution to the expected frequency distribution of English letters. The difference between the observed and expected frequencies will give you a clue to the corresponding plaintext letter.

Finally, combine the decrypted letters to recover the keyword and the plaintext.