See if this link helps. If you want to play the .mp3 files as Music, put them in the Music folder (as noted in the link). If you want to use the .mp3 files for ringtones, put them in the Ringtones folder. You can likewise put them in the Notifications folder if you want to use them for notifications.
As noted in the link in the earlier post, an option is to connect the phone to your computer via the USB cable, then 'drag and drop' the files from your computer to the appropriate folder(s) on the phone.
Once the phone and computer are connected and the drivers load, open the Computer folder on your computer, then double-click the folder for the Turbo (probably listed as XT1254), then double-click Internal Storage.