Simple caesar cipher encryption and decryption

Really simple. Should only take about 30 mins for an expert.
I need to submit a program caesar cipher encryption and decryption – using python.
I have attached the assignment sheet, please have a read and let me know. This is my first assignment and i want to present a good impression. Thank you for your time. Do email me if you have any questions.

The due date for this is 6 of April 11:59pm.