SYNCHRONISING iPHONE AND iPAD

[SAPECA]

As a Premium user of Spotify I expect to be able to download songs onto my iPhone then transfer (or sync) those songs to my iPad. But when I log into Spotify on my iPad with the same email address and password as on my iPhone the songs do not appear and Spotify on my iPad does not show me as a Premium user. Both devices are comunicating on the same WiFi chznnel. I have tried uninstalling then reinstalling the Spotify app on both devices but this did not fix the problem. Can anybody help me?