Starting a project involving Access database

So I'm attempting this project, but have no idea where or how to start. The requirements are as follows:

Design and code a program for a mail-order company that enables a clerk to enter each catalog number for items the customer wants to order. After entering catalog number, the program looks up the item's price, description, and quantity available. When the clerk enters the quantity desired, the program verifies that the quantity is actually available and calculates the total price for that item and added to the order total. The information for the total order will be displayed on a separate sheet.

Any advice would be appreciated.

Thanks!