You may make your complaint via email or snail mail. You will need to also provide the necessary information to validate your claim. You may view the list of information you need to provide here:
There is also a form that you can submit instead of email or snail mail.
For clarity, you retain all of your ownership rights in your User Submissions. However, by submitting User Submissions to YouTube, you hereby grant YouTube a worldwide, non-exclusive, royalty-free, sublicenseable and transferable license to use, reproduce, distribute, prepare derivative works of, display, and perform the User Submissions in connection with the YouTube Website and YouTube's (and its successors' and affiliates') business, including without limitation for promoting and redistributing part or all of the YouTube Website (and derivative works thereof) in any media formats and through any media channels. You also hereby grant each user of the YouTube Website a non-exclusive license to access your User Submissions through the Website, and to use, reproduce, distribute, display and perform such User Submissions as permitted through the functionality of the Website and under these Terms of Service. The above licenses granted by you in User Videos terminate within a commercially reasonable time after you remove or delete your User Videos from the YouTube Service. You understand and agree, however, that YouTube may retain, but not display, distribute, or perform, server copies of User Submissions that have been removed or deleted. The above licenses granted by you in User Comments are perpetual and irrevocable.
The above basically means that as YouTube or any user of YouTube can do anything with your video while it is posted on YouTube.