Different Price for Different Product Size Dropdown

I am a noob on Zen Cart - just installed it 2 days ago and setting it up. Pretty straight forward until now.
What I want to do is have a dropdown on a few products in different categories that have a small size for one price and a large size for another price. Example would be Product 1: small = $6.00, same Product 1 in Large size $9.00. When I use the attributes editor, it either adds or subtracts the attribute price to the base price and after having looked through the forums and read a number of tutorials, I am still confused how to do this. I know it must be very simple, but I am just missing the point here somewhere.
Can someone point me to a simple explanation of how this is done? Sorry for such a noob question - I'm pretty simple minded and easily confused.

When you create or edit the product, set Product Priced by Attributes: to Yes, set the price of the product to 0.00, and set the price for each attribute when you create them.

Thanks Steve! I appreciate the response!