Once you have signed into your account you have many things you can investigate.
To upload a movie you have made....
ensure your movie is saved in one format, I use wmv. You tube will you tube account will advise if this hasn't been done.
Store it somewhere easily accessible, like your desktop.
Click on video manager
click on Upload
Select files from your computer. This uploading can take a while so try to do it when you have finished working online.
Ensure you make it public. If you don't people will not be able to view it without a link. I want to make our videos accessible to everyone. If there is a privacy issue with any children I find ways for them to be on the video but without any pictures. Using an easispeak or puppet theatre are some ways to achieve this. Always consider child rights and provacy issues when loading childrens movies online into a public forum.
When the movie has been uploaded you can retrieve an embedding code to put into a blog.