iTunes works great for me. I downloaded it, iTunes automatically loaded it when the download was complete and and I just had to load it on my phone:
- Make the track a playlist (with track selected in iTunes, select File > New Playlist From Selection) - rename the playlist something like "Walk In The Park"
- With your iPhone plugged in to your computer, select it under devices
- Click on the "Music" tab
- Click the "Selected playlists, artists [etc.]
- Find the playlist you just created under "Playlists" and click the checkbox
- Click the "Apply" button
Yes, there are other ways to do it, but this is what I did.