Your U12 life has a microSD memory card slot. If your personal computer is compatible with that card type (Most laptops are so-equipped), you should be able to save a music file
The HTC U12 life 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 (HTC U12 life-compatible) offered here at MartinsRingtones.com:
Free 'Unclassified' Ringtones Free Ghost Ringtones Free Ringtones-a-gogo Free Techno Ringtones Listen To All Our Free Polyphonic Ringtones