I have 3 urls for a lightsail container, how would I make sure google only indexes one?

Hello.

Looking at the document below, it seems that if you return "X-Robots-Tag: noindex" in the response header, it will not be indexed.
In other words, I thought it would be a good idea to add a process on the application side that would return "X-Robots-Tag: noindex" in the response header when accessed from a domain other than the domain.
https://developers.google.com/search/docs/crawling-indexing/robots-meta-tag

Or, how about configuring the web server (Apache, etc.) to block access from users other than the domain?

<VirtualHost *:443>
    ServerName howtoabroad.com
    DocumentRoot /var/www/html

    SSLEngine on
    SSLCertificateFile /path/to/your/certificate.crt
    SSLCertificateKeyFile /path/to/your/private.key
    SSLCertificateChainFile /path/to/your/chainfile.pem

    <Directory "/var/www/html">

        RewriteEngine on
        RewriteCond %{HTTP_HOST} !^howtoabroad\.com$
        RewriteRule ^.*$ - [F,L]
    </Directory>
</VirtualHost>