Hey, Mary!
I can fix the links you've already put in if need be, but try this first.
If you get your link from YouTube, click on the embed button and copy all that code.
Then, on the blog you'll click on the "Edit HTML" tab when you create a new post (top right) and paste all the code in there. Then, click the compose tab again and write your post.
It should show up with the video/pic embedded on the page!
:)
Amy