There are four basic steps involved in the creation of a Magento configurable product:
Add attributes (such as color or warranty).
Add these attributes to the attribute set. IN this tutorial, I will create and add to the attribute set named Phone.
Create a simple product for each variant of the configurable product.
Create a configurable product and add the attributes to it.
To add the attributes, navigate to Catalog > Attributes > Manage Attributes from the top menu.