How would I go about creating this program? Carpet price calculator.

I'm trying to teach myself a bit more about VB, and I have no clue how to start a program such as this one, it's a carpet price calculator, I created a form myself which allows the user to enter a color, style, and a price per square foot of carpet. On the other side of the form, the user enters the room size data, width, length, area. What the program needs to do is add up the total cost and display it in a text box at the bottom of the form.

Here are just some of the requirements:

Rectangle Class should have the following:

Three Private member variables: Length, Width, Area

The three member variable should have corresponding properties

The Area property should be read only.

CalArea Method (sub Procedure which updates _area)

Constructor which initializes the member variable to 0

5 Carpet Class should have the following:

6 Form should do the following:

Three Private member variables: Color, Style, Price

The three member variable should have corresponding properties

Constructor which initializes the variables to either the empty string / zero.

Declare / create Carpet and Rectangle objects at form level

*Keep in mind i'm not looking for the answer, I just want to know how to start/code a program to do this. I'm completely lost and I'd like to know how to make a program like this one*