The Cadence LTE features a microSD memory card slot. If your personal computer has a slot for that type of card (Most notebooks are so-equipped), you should be able to save music files
The Cadence LTE is equipped with Bluetooth version 4.1 + LE/EDR, which lets you connect to your computer wirelessly. Just pair phone and computer together and drag and drop any music file from your computer to your Kyocera Cadence LTE.
If the above-mentioned tricks fail or if you prefer not to buy new accessories, you can always use one of the numerous free '3G Uploader' services available online. A search on Katapulco should retrieve plenty of them. 3G uploaders work as follows: Transfer your own ringtones on their web site and they will provide a URL. Navigating to that URL with your Kyocera Cadence LTE's browser will download the free ringtone.
Here are links to some of the free ringtones (Kyocera Cadence LTE-compatible) offered here at MartinsRingtones.com:
Free Horror MIDI Ringtones Free Tropical Ringtones Free Ringtones-a-gogo Free Techno Ringtones Listen To All Our Free Polyphonic Ringtones