- Unzip the plugin file.
- Upload with your FTP software the "contact-manager" folder, and only this folder, to your plugins directory (it should be "wp-content/plugins").
- Activate the plugin through the "Plugins" menu in WordPress.
- Personalize the plugin interface through the "Back Office" page of Contact Manager in WordPress.
- Configure the plugin through the "Options" page of Contact Manager in WordPress.
You can also install Contact Manager through the "Install Plugins" page of the "Plugins" menu in WordPress (Plugins => Add New => Upload). Upload the plugin file without unzipping it.