You can easily import external playlists (PLS, M3U and M3U8) by running the Import Playlists script.

This script will let you choose which specific playlists you would like to import (different folders and relative paths is supported).

During the import Helium will check if the files contained in the selected source playlists exists in the library and if not they will be added automatically.

After all files are ensured to exist in Helium library, the playlists will be created and the tracks will be added to them.