This Plugin sends alerts to a given email address when someone logs into your wordpress instance
Go to your Wordpress Admin Page and click on Plugins. Click on install and on upload Plugin on top. Download the Zip here at RELEASE and upload the zip at your Wordpress page Then activate the Plugin. Go to the Settings-Page of the plugin and enter your Email adress to get the Alerts.
You need to install https://wordpress.org/plugins/wp-mail-smtp/ first
Use at your own risk