How to enable https on IIS 8.0?

I am using IIS 8.0.9200. In my local computer - I want to set up the https enable sites means site which I currently run must be run over https(SSL). For that when I seen in BINDINGS of website – where type drop down which shows http/https settings, in my computer it is always seen as disabled on add/edit mode. I am using windows 8.1 version.

so how to make enable that dropdown to make https? and what are the next steps then to achieve that?