Please elaborate a bit more as if you are referring to Phone/Tablet layout versions of site which you want to add to your Muse site.
These links would be helpful :
http://helpx.adobe.com/muse/tutorials/creating-mobile-layout-designs-muse.html
http://tv.adobe.com/watch/muse-feature-tour/adobe-muse-designing-for-smartphones-and-table ts/
https://www.youtube.com/watch?v=_Bq1hViogS4
Thanks,
Sanjit