You can input data on the SiteMap filed, in the import site tool. You need to input space indented organization for your site, like the images bellow:
Now, to generate reusable components... This is a lot more hard. You see, there is already a lot of components ready to use, you only need
to include a parsys on your imported site then you can use the ones that Adobe/Day already build for us. However, I do not recomend to you work with imported sites, because it will be a lot hard to edit the pages design as you wish. This is an advice that someone gave me here in the forums weeks ago and now I can, by experience, tell to other people.
There is a easy way to create e website starting from an already build website content, and you can see this guide here: http://dev.day.com/docs/en/cq/current/howto/website_quick.html
You need to use CQ5.4 to do step by step on this guide, because of the Content Loader that is no more on the CQ 5.5
Anyway, good luck with your project.