Hi Shelly,
The WordPress added this in 4.5 and you can change the label in two ways:-

1. Translating WordPress
2. Using code

Do you want to disable login with username completely or just text? If your intention is to disable login with username, I will suggest looking at email login plugin.

Regards
Brajesh

Hi Shelley,
Thank you.

In that case, you may use this code in your bp-custom.php

/**
 * Filter and translate the WordPress login text label.
 *
 * @param string $translation translation.
 * @param string $text original text.
 * @param string $domain text domain.
 *
 * @return string
 */
function buddydev_filter_email_login_label( $translation, $text, $domain ) {
	if ( 'Username or Email Address' === $text && 'default' == $domain ) {
		$translation = 'Email Address';
	}

	return $translation;
}
add_filter( 'gettext', 'buddydev_filter_email_login_label',10, 3 );

Regards
Brajesh

Hi Shelly,
It should be in your public_html > wp-content > plugins assuming that public_html is where all the fiiles for community.pointlomatowncouncil.org is hsted.

Regards
Brajesh

You are welcome.