http://en.wikipedia.org/wiki/HttpsBut, to give you a brief summary of the situation, the server already has support for it (as far I can notice). so, all that is needed to be done is to direct traffic on https comming to ouer url to the site files, and possible get a certificate (unsure if you can skip that part and run pure on ssl). I will update in here later about that.
https make a ssl handshake, put some cryptation on the traffic and prevent simple sniffers from seeing passwords and username.