If a playlist has been shared by your organizational unit's manager, you can pull content into your playlist at any time.
Click on the 3 dots, then Import content from a playlist:
You will then see the shared playlists that are available to you.
Select the playlist you are interested in, then the content you want to import.
Click on Save and the content will be added to your playlist. This content remains linked to its original playlist: as soon as it is modified by your OU manager, the modification will be reflected in your playlist.