Add a message to the WordPress login page footer area.

wp-login-footer-message.php

<?php
/**
 * Adds a message to the footer area under the login form.
 */
function hd_login_footer_message() {
	
	// output our message in the login footer area.
	?>
	<p style="border-top: 1px solid #0085ba; margin: 0 auto; width: 320px; padding-top: 10px;">Use your @highrise.digital email address to login here.</p>
	<?php

}

add_action( 'login_footer', 'hd_login_footer_message' );