If you are adding your simple products to a configurable product, then you only need to merchandise the configurable product, this is unless the configurations (simples) have different product images for each option OR your configurations have different prices.
Typically configurables are used for items with varying sizes / colours that are all the same price. For example, a T-Shirt, available in S,M and L and Red and Blue, all options would be the same price but have different attributes.
In the instance of Ashbrook Roofing, we will be using configurables in a non-conventional way. Code 3 lead for example has 2 different attributes (width and length) and each option has a different price. In this case, the simple products need to contain the prices and the configurable will read those prices.
Again Navigate to Add Product and click the drop down to select "Configurable Product"
The page will look identical to that of a simple product but if you scroll to the bottom you will see a tab called "Configurations". Expand this view and click Create configurations. The following screen will be displayed:
If the attribute you require is not displayed (it has not yet been created, e.g Length or Width) then click Create New Attribute
Default Label - This is what your attribute will be named e.g Length or Width
Catalog input type - This is how you would like the option to display, dropdown, radio button, text field etc.
Value Required - Do you want this attribute to be a mandatory field for all products?
Then click Add Option and you can begin adding your options eg 100mm (4"), 150mm (5")
Advanced Attribute Properties
Attribute code - (same as the name but lower case)
Scope - If you have more than one website or store and want it applicable to all, set to global. Attributes can be website or store specific too.
Then click SAVE ATTRIBUTE
It will take you back to the first screen only now your attribute appears in the list for selection. Tick it and then click Next
Then select the options that are applicable to this product (If it is colour and your colour attribute has hundreds of colours but this particular item only comes in 3 colours, just tick the 3 relevant colours).
On the next page, all options will be set to Skip (Skip adding images to each simple, skip adding a price to each sku, skip adding a quantity, unless all of the products with that attribute have the same price or quantity etc - most likely you will skip this every time.
Magento will then show you a summary of the options it is going to create based on your attributes. Then click Generate Products and your options will be added.
You will be returned to the main product set up page and the options will be there, you then need to add quantities and weights to each simple and change whatever details you want. If the simple already exists in Magento then click Actions > Select > Choose a different product, and you can search for the one you are looking for.
Save and close, et Voila!