From the web, you can create a Playlist by clicking on the action menu and selecting Add to Playlist.
A popup will appear where you can add the song or album to an existing Playlist or select 'New Playlist...'. If you're creating a new Playlist, just add a name and description to your new playlist and click Create Playlist.
You can also drag and drop a song or album into a playlists shown in the left-hand sidebar.
Allow other people to add and modify music on your Playlists by making them collaborative. Once you've created a Playlist from the web, select the Playlist in your left-hand sidebar, or select it from your Profile's Playlists tab.
Once you're viewing the Playlist, select 'Edit', then choose from Collaboration Off, Open to people you follow, and Open to everyone.
On each Playlist, click the Edit icon, and you’ll see an option that says Privacy. If you want your playlists to show up on your profile and in search results, click the box next to Public.
Drag a track to move it up or down within your playlist, or click the "x" on the far righthand side to delete songs from your Playlist entirely.
Custom Playlist artwork
To upload your own playlist cover art, hover over the playlist's current cover art, and select the "edit" pencil.
You'll see a pop-up with the option to "Choose File"—use this to add your image, and hit Submit!
A square image will work best, otherwise, Rdio will automatically crop the image to fit.
Deleting a Playlist
To delete a playlist, click the Edit icon. Then, click the "Delete Playlist" in the bottom left.