how to convert http to https easily ?

do check this link:

https://newevolutiondesigns.com/convert-http-to-https

you also need to generate certificate for it :)

http or https configurations are done in web server, I assume that you are using IIS web server.
Please see below link to configure https website:

For IIS6:
http://www.sslshopper.com/article-how-to-configure-ssl-host-headers-in-iis-6.html

For IIS7:
http://www.sslshopper.com/article-ssl-host-headers-in-iis-7.html