1. plug phone into computer
2. swipe down the notification bar and choose the icon that just came up
3. choose the disk drive option
4. open my computer and select the removable storage drive
5. create a folder called media
6. in the media folder, create a folder called ringtones
7. copy whatever ringtones you want into that folder
the files you put in that folder will now show up in the ringtone selection popup when you go to change it.
if they don't, reboot the phone and they will show up.
in the media folder you can also create a folder called notifications and put whatever sounds you want for notifications in that folder and do the same thing.