Connect to HTTPS web service

My Unity App connects to a web service using http protocol. I need to know what I have to change when connecting to a web service but using https protocol, instead of http. I suppose I have to include the server certificate (UNTRUSTED, own signed) in my Unity App, but I don't know how. I connect to my web service using WWW class and parsing the result manually. Thank you very much in advance.

Santy