Find "Music"
Press the menu icon.
Press Music.
Create a playlist
If required, press the library icon.
Press Playlists.
Press Create new playlist.
Press the required audio files to add them to the playlist.
When the box next to an audio file is ticked (V), it's selected.
Press Create.
Key in the the required name and press OK.
Exit
Press the Home key to return to standby mode.