Your Asus Max Zenfone 4 ZC520KL 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 Asus Max Zenfone 4 ZC520KL is a smartphone. Most smartphones will let you save any song found online by tapping and holding your finger on it, then selecting 'save.' Once a music file is saved to your media library, tap-and-hold it and select 'assign' from the drop-down menu.
The Asus Zenfone 4 Max (ZC520KL) 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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