Adding Music to Plexamp

I have installed Plexamp on my iPad and would like to add music or create playlists from my music library already on my iPad.
I cannot see any way in which I can do this. Can anyone tell me if this is possible please?

Plexamp plays music from a PLEX server. Do you have a PLEX server?

Yes I do. It is on a windows pc. Am I correct in assuming from your comment that I need access to the server, either by wifi or remotely, in order to play on my iPad using Plexamp?
If that is the case then I would only be able to do this when at home as I cannot access the server remotely.

Correct. Plexamp is not a standalone music player. Think of it as a Plex app that is optimized for music.

Ok. Thank you very much for clarifying that for me.