Yes, you can save someone else's Spotify playlist. Here's how you do it:

1. Open the Spotify app on your device.
2. Use the search function to find the playlist you want to save. You can search for the playlist if you know its name or you can search for the user who created it and find the playlist in their public playlists.
3. Once you've found the playlist, click on it to open it.
4. You'll see a heart icon or a "follow" button at the top of the playlist next to its title. Click on this button.
5. The playlist is now saved to your library! You can access it anytime from your library under 'Playlists'.

Remember, you won't be able to edit the playlist or remove songs from it, as it's someone else's playlist. But, you can create a new playlist and add the songs you like from the saved playlist to your own.