Your Aristo 2 has a microSD memory card reader. If your personal computer can also read that card type (Most laptops are so-equipped), you should be able to save a music file (The LG Aristo 2 supports these formats: Yes) from your computer to a microSD memory card, and then, from the memory card to your LG Aristo 2. Your manual should tell you how to assign the file to your phone's main ringtone.
The LG Aristo 2 is an Android phone and there are plenty of free ringtone apps such as MP3 Cutter, RingDroid (open source) and more.
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