If it's an S 3 then it probably has Android as the operating system. In that case find the button that brings up the menu and go to settings. Go to storage or memory then view the available space. Usually there is a choice to adjust where you can save things like pictures and it will be either on the phone or the external card. If you connect a usb cord to the phone and open on a pc the path will usually be Androidmediamusic or something like that. Just copy and paste music to the file and disconnect the phone and try to use the phone menu to navigate to music. You might need download a music player to the phone of it already doesn't have one. Most androids or i phones already have them but sometimes they are not made to work with the type of music files that your installing. In any case you might need a file converter. If it all sounds to complicated just take the phone to the place you got it and most good sales personnel will show you.