Click to launch iMovie from your dock.
Select your project from the Project List on the left side of the screen.
Select YouTube... from the Share Menu.
Click the Add button to add your YouTube account.
Click the Sign In... button to sign into your YouTube account.
Your web browser will open to the YouTube signin page. Input your Username and Password then click the LogIn button.
You will then be notified that iMovie would like permission to upload videos to your account. Click the Allow button.
Return to iMovie and click the Confirm Sign In button.
You can now set the Category, Title, Description, Tags, Size, and Privacy of the movie.
Input these values then click Next button.
You will be asked to accept the YouTube Terms of Service. Click the Publish button.
Your video will then be published to your YouTube account. Once your video is uploaded to YouTube you will be notified of its YouTube address. You can also tell a friend or view the video.