To add a video to a playlist (or create a new playlist), click the "Playlist" button on the bottom of a post. Once you have a playlist, it will appear under the new "Playlist" link in your profile. (Where there is currently"All, Videos, Photos").
You can easily add videos to playlists, re-order the videos, etc... If your playlist contains videos from other models, a link to their profile pages will appear under the playlist.
Users see the videos or just previews based on whether they are subscribed to the model (this also works with Tiered Pricing).