The BLU T430X features a microSD memory card reader. If your personal computer can also read that type of card (Most notebooks are so-equipped), you should be able to save music files
The Tank 3 is equipped with Bluetooth version 3.0, 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 BLU Tank 3.
If the above-mentioned approaches 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 BLU Tank 3's browser will download the free ringtone.
Here are links to some of the free ringtones (BLU Tank 3-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