The Asus Pro Zenfone 4 sports a microSD memory card reader. If your laptop or personal computer can also read that card format (Most notebooks are so-equipped), you should be able to transfer music files
The Asus Pro Zenfone 4 is a smartphone. Most smartphones should let you save any mp3 song available online by touching and holding your finger on it and selecting 'save.' Once a music file is stored on your library, touch-and-hold it and choose 'assign' in the contextual menu.
The Asus Zenfone 4 Pro is an Android smartphone and the Android market offers a bunch of free ringtone apps such as MP3 Ringtone Maker, Zedge and more.
Here are links to some of the free ringtones (compatible with your Asus Zenfone 4 Pro) we offer:
Free Horror Ringtones Free Tropical Ringtones Free Ringtones-a-gogo Free Techno Ringtones Hear All Our Free Polyphonic Ringtones