The Xperia XA1 has a microSDXC memory card slot. If your personal computer has a slot for that card type (Most notebooks are so-equipped), you should be able to save music files
The Xperia XA1 is a smartphone. Most smartphones will let you save any mp3 song available online by touching and holding your finger on it, then selecting 'save.' Once a music file is stored on your library, tap-and-hold it and select 'assign' in the contextual menu.
The Sony Xperia XA1 is an Android phone and there are plenty of free ringtone apps such as MP3 Cutter, Zedge and more.
More on free ringtones
Here are links to some of the 100% free ringtones (Sony Xperia XA1-compatible) offered here at MartinsRingtones.com:
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