The R11s Plus is equipped with a microSD memory card slot. If your laptop or personal computer is compatible with that kind of card (Most notebooks are so-equipped), you should be able to transfer music files
The R11s Plus is a smartphone. Most smartphones let you store 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, all you have to do is, again, touch-and-hold it and choose 'assign' in the contextual menu.
The Oppo R11s Plus is an Android smartphone and the Android market offers a bunch of free ringtone apps such as MP3 Ringtone Maker, Zedge and more.
Learn more about making your own free ringtones
Here are links to some of the all free ringtones (compatible with your Oppo R11s Plus) we offer:
Free 'Unclassified' Ringtones Free Tropical Ringtones Free Ringtones-a-gogo Free Techno Ringtones Hear All Our Free Polyphonic Ringtones