Use the automatic installer in your WordPress dashboard > plugins > add new. Search for Speakout!
follow the instructions.
Or you can:
- Download the zip file from the plugin’s WordPress.com respository
- Unpack the file
- Upload the “speakout” folder to your “/wp-content/plugins/” directory
- Activate SpeakOut! Email Petitions through the “Plugins” menu in the WordPress dashboard
- Add a petition