WordPress.org

Install through backend:

1. Search for email commenters.
2. Click install.
3. Click activate.
4. Look at your posts, you should have a new email icon in the toolbar.

Install manually:

1. Unzip the email-commenters.zip file.
2. Upload the the email-commenters folder (not just the files in it!) to your wp-contents/plugins folder.
3. In your WordPress administration, go to the Plugins page
4. Activate the Email Commenters plugin.
5. Look at your posts, you should have a new email icon in the toolbar.