Assuming you do not have any video editing program eg Movie Edit Pro, Video Pro.
You can add a video clip to an arranger track in Music Maker and export the video + audio from the arranger as an AVI or WMV video file, Music Maker does not support other formats that YT does, then use Youtubes own uploader.
Keep a backup copy of the video you upload in case of loss etc.
There is more information in the PDF manual available under Help.
Ensure you use a supported format ie .avi, .wmv, .asf, or .mov