How to Hide WP SendGrid Mailer Admin Menus

function plt_hide_wp_sendgrid_mailer_menus() {
	//Hide the "SendGrid Mailer" menu.
	remove_menu_page('wp-mailplus-settings');
	//Hide the "SendGrid Mailer → Settings" menu.
	remove_submenu_page('wp-mailplus-settings', 'wp-mailplus-settings');
	//Hide the "SendGrid Mailer → Logs" menu.
	remove_submenu_page('wp-mailplus-settings', 'wp-mailplus-logs');
}

add_action('admin_menu', 'plt_hide_wp_sendgrid_mailer_menus', 11);

Where do I put this code?