i went to manage applications then i click the youtube but i cant click the uninstall button,. i can only click the clear data and clear cache on it.
Welcome to our AndrioidForums, eureckachin--glad you signed-up with us

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As Rukbat said, if you don't have the uninstall or disable function in the stock Settings -> Apps or Manage Apps menu, then you'll have to root your phone in order to be able to remove those applications.
You should know that:
1. It's always better to disable (also called "freeze" or "freezing" them) than it is to delete [this keeps the app in-place / on your device but simply disables it from being run / launched.
2. It's always better to rename than delete. Renaming allows you to (fairly) easily rename it back should you need to.
3. If you do actually delete it, make sure you've taken a Nandroid backup (root-only and custom recovery only function) before doing so--you don't want to end-up with a boot loop or soft bricked device.
You'll want to visit your device's all-things-root area,
Ace - All Things Root - Android Forums, for detailed and device-specific instructions and guidance re. the above.
Cheers and best of luck!