WordPress.org

1. Download the plugin.
2. Copy it onto your website in the wordpress `/plugins` folder. Then enable the plugin. That's it. Wavatars will instantly appear for all posts (even old ones) on your blog. If you don't like how the image looks within your theme, read on...

The administration panel is under Options » Wavatars. You can adjust the size of the Wavatars, and assign HTML to come before and after each image to help nudge it into place. Each image is also set with the CSS "wavatars" class. On my own site, I don't have any HTML prefix or suffix, and instead just added these lines to my CSS:

.wavatar {
    float:             left;
    padding:           3px;
    background:        #fff;
    margin-top:        -25px;
    margin-left:       -25px;
    margin-right:      5px;
}

If that still doesn't give you enough control over wavatar placement and you don't mind editing your theme, just turn off automatic placement and add the line wavatar_show($comment->comment_author_email); to your comment loop wherever you want the image to appear.

Your mileage may vary. How it will look depends largely on your current theme.

Note that the plugin requires that your install of PHP support the GD library. If it doesn't, the Wavatars won't show up and you'll get a warning in the Wavatar admin panel. You can still use this plugin to display Gravatars, even if the GD library isn't available.