How to add meta tags into posts: description and keywords

Hello there,

I really hope someone can help me with this.

This is my site’s test blog: http://www.mercamgf1-fans.com/petronas

If you see under latest news there are multiple posts. What I want is that the summary there appears as a meta tag of keywords and appears on the single post after a description of the post. The description (meta tag of description) would be a short sentence. Font size of the summary of the post on homepage view is 12px, but the default font size in single post is 11px. I want that the description in the single post is bold and 12px.

To not get confused, I made a preview shot:
http://i382.photobucket.com/albums/oo270/taddy1449/meta-tags-explain.png

I’m actually refering to this site’s article(that’s what i want):
http://f1.rtvslo.si/index.php?id=news&type=novice&item=6221
by viewing the page’s source you can see what is the description and what are keywords.

I have read the tutorials and articles about meta tags for wordpress here on wordpress.org, but I couldn’t get it working as I didn’t quite understood it. Very confusing.

Would really appreciate any of your help,

thank you