Plug your phone into the usb port on your computer.
When you see the USB icom in the top left corner, pull it down, you will see "USB connected" Tap on that and then tapon "mount" you can now access your phone as a removable disk drive and drag your music files onto the phone.
After you have you songs , when the one you want is playing, bring up the options menu and touch "use as ringtone" and that song will be your ringtone.
Sure can. Do the same as stated above on mounting the removable disk, but this time make a folder called "ringtones" (this also works for "notifications" and "alarms") and drop whatever supported music file type you want there. Now when you go to the contact, pull up the menu, and select options, your ringtones will be in the list to choose from.