How to play local itune files on spotify mobile device

[muse_surfer]

I am a premium user. For the past several years I have used mostly spotify on my desktop. I have several playlists where I combine spotify tracks along with local files from my iTunes library. This works great for my desktop, however I'm trying to figure out how to accomplish the same thing on my mobile devices. When I open these same playlists which combine spotify tracks and iTunes tracks on my iPhone or iPod, all the local iTunes tracks are greyed out even though these local tracks exist on the mobile device.

The phone app gave me some instructions about making the playlist available for Offline Sync? This was supposed to allow me to play the greyed out tracks if I owned the songs.  So with my phone and my desktop on the same Wi-Fi network I made the playlist in question "Available Off-Line" on both devices, but it did not work.  I see no option with the exact wording of "Offline Sync". Just "Available Offline"

Please help,

Thanks