This is how I added a video on my wordpress blog post (http://bisdak.dpjonline.com)

1. Login in to your WP Dashboard.

2. Click Plugins

WP Plugins Window

3. At the new plugins search for youtube

search

4. Look for the youtuber plugin

youtuber

And click the install link at the right most.

5. After the installation click on the activate plugin button

activate

6. Add or Edit your post and insert this line

youtuberx

anywhere in your post where xxxxx is the youtube video ID.

Good Luck and More Power!!!
http://www.dpjonline.com