Your BLU S-1 has a microSD memory card slot. If your personal computer has a slot for that card type (Most laptops are so-equipped), you should be able to save a music file
The BLU S1 is an Android phone and there are plenty of free ringtone apps such as MP3 Cutter, RingDroid (open source) and more.
More on free ringtones
Here are some of the 100% free ringtones (BLU S1-compatible) offered here at MartinsRingtones.com:
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