Just following next steps:
(1) Run Youtube Movie Maker, select "Make Youtube Video" Mode.
(2) Press "Source Videos button" or “Source Photos button” and then press "Add Source Button" to add all source videos or your taken photos into Youtube Movie Maker, and you will view all videos or photos in source files list.
(3) Then directly drag and drop videos and phtos into Timeline from the source file list, or you can press "Add to TimeLine button" to add videos and pohtos into Timeline from the source file list, then you will view them in Timeline,
(4) At last, you can press "Preview button" to preview the made video, press "Publish To Youtube button" to publish the made video on Youtube.com, or press "Save To Local button" to save the made video to computer hard drive.