- From your admin interface go to Plugins > Add New
- Search for unspam
- Click "Install Now" under the plugin in the search results
- Click OK on the popup
- Click "Activate" to enable the plugin
- Unzip the installation zip file
- Copy the files to your plugins directory (via FTP or whatever)
- From the admin interface click Plugins
- Find the plugin in the list of plugins and click "Activate"
Currently there is no configuration on this plugin.