Sure, here are the steps to make your Spotify playlist private:

1. Open Spotify: You can do this on your desktop app or mobile app, whichever you prefer.
2. Navigate to Your Library: This is where all of your playlists are stored.
3. Select the Playlist: Find the playlist you want to make private and click on it.
4. Go to the Playlist's Settings: If you're on desktop, you'll find this by clicking the three dots (...). If you're on mobile, you'll find this by tapping the three dots in the top right corner.
5. Make the Playlist Private: On desktop, click 'Make Secret'. On mobile, toggle the switch next to 'Make Secret'.
6. Confirm: Your playlist is now private. Only you can view and play this playlist.

Remember, Spotify may update its interface or procedures over time, so these steps might slightly vary. If you can't find the settings or options, look for similar terms or icons.