How does one find it on a server?
(no I'm not going to do anything stupid, I just want to know how it's accessed.

I'm guessing your after curl compiled with PHP

make a .php which contains

<?php print curl_version(); ?>

If it doesn't say undefined function curl_version that curl is compiled with php, but if you are after it for https (using it with things like egold, etc), then make sure someone in the output it mentions OpenSSL.