WordPress.org

1. Upload the plugin files to /wp-contents/plugins/calais-auto-tagger directory
2. Activate the plugin through the 'Plugins' menu in WordPress
3. Add your Open Calais API key through the 'Calais API Key' sub-page of the 'Settings' menu

To obtan a Calais API key:

1. Go to the Open Calais website at http://opencalais.com/
2. Click "Register" at the top of the page and create an account
3. Request an API key at http://developer.opencalais.com/apps/register

You should receive the key immediately.