Answer:
Shift the entire alphabet by the number you picked and write it down below your original alphabet (as shown above).
Pick a message to write to your friend. ...
Write down your encoded message using your shifted alphabet. ...
Give your friend the encoded message and tell them the key.
Explanation:
Caesar cipher is a very simple encryption method and is easily cracked if one studies the frequency of repeating letters. To improve the strength of the encryption method a more complex key could be used. Instead of shifting by 1, a pattern of shifts could be used: For example, 1,4,5,1.