Analyse sales performance using simple code

My small company wishes to analyse the performance of its salespeople over the first six months of the year and also to compare performance from one year to the next. I have attached my attempt but none of us know how to ask the programme to take in our results only output them. I need someone to design and write a program to read each month’s sales amount, from January until June for the past two years, and to generate the required statistics, along with averages in simple understandable coding as we will need to edit it ourselves later.