1- Click on “Playlists” in the left vertical menu. This will load all of your playlists and also the public playlists.
2- Click on the playlist that you want to edit, under “Your Playlists”. This will load the Playlists detail page as below.
3- Click on “Edit’ button in the right, above the Playlist thumbnail list. This will load the Playlist Edit page.
4- On the Playlist edit page, you can change the video order by dragging the thumbnails in right with your mouse.
5- You can click “Save” once changes are made. This will take you back to the Playlist detail page with the updates.