I Give Up - How to add to a playlist in LMS?

Has to be the worst music managing software ever written.
I was able somehow to create some playlists but am at a complete loss how
to add anything to them.
I assume the playlist has to be open on the right side of the screen but can't
find any way to make that happen.
Thought maybe I could do it in iPeng but struck out there too.

Really appreciate any step by step info on how to do it!

Thanks,

Carl