Think of your first configurable product: what will customers view on the BTO configuration page? That is: what should they be able to pick on that page? Write down items and the groups in which they should be organized, then proceed as follows:
Add a “Category” in the ProductCart catalog for each of the groups you wrote down
Add some products to each category.
Read this section to learn about Standard Products and BTO-Only Items
Now create the BTO product, which is just like creating any other product, except for a few fields that you can ignore
After saving the BTO product, click on the configure link to assign categories and products to it.
Yes, that's correct. For example, a gift basket might contain a product for which the customer needs to select the right size/color (e.g. a t-shirt that is part of a “Corporate Gift Basket”). To assign an Apparel product to a Build To Order product, do the following:
Create an “Apparel” product (add a new product and set it up to be an “Apparel” product using the area at the bottom of the page)
Assign options to it and generate its “sub-products” based on those options
Create a “Build To Order” product
Click on the “Configure” link to start assigning selectable items to this Build To Order product
Assign the “Apparel” product to the BTO product
Now preview the page: you will see that you can change the options that have been specified for that “Apparel” product (e.g. color or image printed on a “Mouse Pad” that is in the “Accessories” category on the configuration page for a customizable desktop PC).
The combination of the BTO system and the Apparel Add-on is very useful when it would not make sense to have the individual product variations show up on the configuration page as individual products (e.g. dozens of variations of the same mouse pad, in the example above).