Add Media

You can easily do that in the Page or Post Write Panels (Pages > Add New, Posts > Add New) or the Edit specific post link or page link panel – With the Add Media Icon – #2 image in guide here – http://en.support.wordpress.com/uploading-documents/

How can I import media from Movabletype?

Ok that’s another matter entirely. I remember importing a Movable Type blog two years ago, but that was a different way entirely and I found it via Google 🙂
Check this out – http://www.simonecarletti.com/blog/2009/02/movable-type-to-wordpress-importer-utilities/ – this seems to be the latest article about importing and could probably help you.