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*NEW 2012*
STEPS BELOW:
1. Creat G-Mail Account
2. Click Your name in the top right corner
3. Go to "YouTube Settings"
4. Click The tab "Overview"
5. Click "Revert to username"
6. Then creat your username
7. Check the box that says you know your going to be changing your username.
8. Your YouTube Username was succesfully changed.