In the list of notes ("All Notes" or an opened folder), touch and hold a note.
The list switches to selection mode. Check the notes you want to move or copy, then use the icons at the top of the screen: "Move Note to Another Folder" or "Duplicate note". A duplicated note is created in the same folder, so move it afterwards if you want it in a different folder.
You can also tap the folder name on the note editing screen to change where that note is stored on the "Select Folder" screen.