How to add music on the existing playlist?

[Peterpetram]

I have 80 songs in my phone i want to add some 20 songs on the existing to make a total of 100. I have tried in vain cause i'm using different computer.

 

[kch50428]

You can't sync to more than one computer/iTunes library... if you've purchased the tunes you want to add in the iTunes Store... or they are in your iTunes match library - just download to your device.