First, get familiar with howto avoid flooding aggregators.

Into ikiwiki, from another CMS

1. Copy content into ikiwiki, taking care to:
   1. Match article paths to preserve old permalinks.
   2. Match enclosure paths (or use redirects) to preserve old URLs.
   3. Match titles, post dates, and guids with [[!meta ]].
   4. Match feed paths with permanent redirects from old Atom location to index.atom (likewise for RSS).
   5. [[!inline ]] the articles.
2. Rerun ikiwiki --setup.

Within ikiwiki, from basic to fancy

1. Exclude media files from [[!inline ]].
2. Replace direct [[WikiLinks]] to media files with [[!meta enclosure="WikiLink/to/media.mp3"]].
3. Rerun ikiwiki --setup.