Wow was this a HUGE pain in the @** ok first download any mp3 ringtone you want or have to use etc. Plug your Samsung Galaxy Centura into your computer using the provided usb cord. Ignore the pop up window when asked what you want to do. I'm using windows 7 so open the download or piece of music etc that you want to use as you ringtone with windows media player. In the top right corner of the screen that's playing your tone/song hover over the 3 little squares with the back arrow it says switch to library click it or the song will finish playing and then you can click go to library. Once in the main windows media player library screen on the right you will see your song/tone/mp3 in blue under unsaved list. Right click on your songs/tone/mp3 name and choose open file location. Once file location is open your song/tone/mp3 will be highlighted in blue. Now look to the left list you will see your phone, mine starts with SCH- go over and left click the little arrow to the left of the SCH (your phone) to expand your phones files. I have a microSD card in, so I have 2 expansions under my phone SD Card and USB storage, if your USB storage folder isnt already expanded, click USB storage now and a drop down will appear
Finally left click you highlighted song/tone/mp3 hold it and drag it over to ringtones. If you want it for a personalized notification left click hold and drag it to notifications. Now look on your phone system settings click sound then phone ringtone. your ringtone should now be there, click on it hit ok to set and BAM!!! your done. Same for Notifications, if you drug your song to notifications go to settings, sound, notification and it's there. Hope this helps someone because I was ready to pull my hair out literally, why they make this so much harder and confusing than it has to be. Enjoy!!!!