There is a massive amount of SEO plugins available for WordPress. Our favorite is the extremely popular "All in One SEO Pack" - http://wordpress.org/extend/plugins/all-in-one-seo-pack/. It's robust but still simple enough for the SEO beginners. To get it setup on your blog:
- Login to your WordPress installation
- Click "Plugins" > "Add New"
- Search "All in One SEO Pack"
- Find it and click "Install Now"
- Click "Activate Plugin"
- Click "Settings" > "All in One SEO"
- Change "Plugin Status" to enabled
- Fill out your Home Title, Home Description, and Home Keywords
- Uncheck "Use no index for Categories"
- Click "Update Options" and the bottom.
- To use it just go into the page/post you want to add keywords / description for in WordPress and you should see a "All in One SEO Pack" panel somewhere under your text editor.
- Hint: Titles will automatically be added so you don't necessarily need to change these.
That's it! :)