How do I pick which songs to put on new ipod?

I just bought the newest nano and hooked it up to my old playlist. Itunes then randomly picked songs from my music library and uploaded it to the ipod. I cannot figure out how to delete songs and switch songs individually on the new ipod because it did not make a new ipod playlist. I can add entire playlists, abut I cant figure out how to individually choose which songs to put on it. Can anyone help?