Your LG Stylo Plus 3 features a microSDXC memory card slot. If your personal computer has a slot for that type of card (Most laptop computers are so-equipped), you should be able to save music files
The LG Stylo Plus 3 is a smartphone. Most smart phones let you save any music file you could find online by touching and holding your finger on it, then selecting 'save.' Once the music file is added to your memory card, tap-and-hold it and select 'assign' from the contextual menu.
The LG Stylo 3 Plus is an Android phone and there are plenty of free ringtone apps such as MP3 Cutter, Myxer and more.
The LG Stylo Plus 3 is compatible with the 'USB Mass Storage' norm. Get a USB cable (There might be one in your LG Stylo 3 Plus package) and, linking your LG Stylo 3 Plus to your computer should make it appear as a memory key. Open it and just drag MP3 songs or other sound or music files directly to your LG Stylo 3 Plus, as if it was one of your computer's folder. For the remaining steps, please refer to your LG Stylo 3 Plus manual. The ringtone section should explain how to select an uploaded file as a ringtone.
Here is a sample of the free ringtones (LG Stylo 3 Plus-compatible) offered here at MartinsRingtones.com:
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