To update a published iMix, click the arrow next to the playlist. You can also edit the description or title of an iMix, or remove an iMix from the iTunes Store.
Here are ways to change your published iMix:
To update an iMix, select the playlist, click the arrow to the right of the playlist, and then click Update. Make your changes and click Publish.
To see your iMix as it appears at the iTunes Store, click the arrow to the right of the playlist and then click View.
To see a list of the playlists you’ve published or to remove an iMix from the iTunes Store, sign in to the iTunes Store and click View Account.