MP3 tracks transfered to Spotify problem

[MitchLuijks]

I transfered about 150 songs from a folder on my desktop to my "SlamFM" playlist in Spotify. The problem is that Spotify doesn't synch these tracks on my iPhone's playlist so I can only listen these tracks on my laptop but not on my iPhone. When I connect both devices on thesame network, it will only synch songs wich I found in Spotify (+ playlist I'm following). How can I solve this problem?

[Peter__]

So it will transfer all of the Spotify tracks apart from those local files? Is your device showing under "Devices" in the Spotify client?

Peter