How to make any MP3 to be used as a ringtone on Android.

Getting your Android phone to use your Youtube MP3 as a ringtone is very easy. Android will recognize virtually any sound file as a valid ringtone, so MP3 works straight out of the box, no conversion to a “ringtone file.”
Start by connecting your phone to your PC. You then create a “Ringtones” folder in your root directory of your SD card—that is, if you don’t already have one there.
When you create or find this folder, simply drop in the converted Youtube.mp3, or any MP3 into the folder.

This HTC Evo Shift took a few extra moments to add the Metal Gear sound to the list of ringtones, but it finally did. You can change the ringtone under the “Sound and Notifications” item in the settings menu.