Do you want to know how to edit youtube video? Until recently, we used to download the youtube video, edit it using windows movie maker and upload it to youtube again.
However, In June, Youtube released an experimental YouTube Editor that lets you do some very basic video editing like trimming the video, adding an audio to the video and giving it a good title. Thus you don’t even have to download the youtube video or convert it to wmv format, to edit it! Moreover, the tool, which requires no additional software, or browser plug-ins (besides Adobe's Flash), lets users make minor edits to videos they've uploaded.
Read on to see how to do it.
Step 1: Upload
You can't actually do this through the youTube editor - they need to be on YouTube before you even begin. If you're new here, that involves hitting the large "upload" link on the top of the YouTube home page.

Step 2: Arrange
Once here, you'll see a listing of your videos in chronological order.

To add clips to your video you can drag them from the "my videos" section, down to the time line, or you can hit the plus icon that's in each clip's top right hand corner. In case you're not sure what a clip contains, you can mouse over it and hit the play icon to watch the whole thing without leaving the page.

Step 3: Cut
YouTube editor lets you trim a video, but not split it, so if you want to cut a single clip into two or more parts you need to drag more copies of that video down into the time line.

Step 4: Publish
When you're done, just give your work a title and hit the publish button. This takes you to the same screen you'd see if you went into the "edit video" dialog.
Youtube video editor is cool to mix and match videos and add some cool audi to it. It probably lacks the video effects but is still an effective online tool to edit YouTube videos. Enjoy the online youtube video editor!
Related Guide: How to download videos from youtube, google, veoh, etc on Mac?