is cURL already installed on the server? php has to be built with curl support, for that you just need to add the --with-curl=/path/to/curl during compile.
I had an issue with cURL picking up my SSL libs, so if you have similar problems let me know and I'll dig up the config files (I hope I still have them...)
Be sure to check the install / config logs to make sure it's all going well. Once you have it installed, phpinfo will outline curl support.
Regards,
Mustafa