First i tell you the mean of HTTPS.
HTTPS increases the security by encrypting the content that are served over the network. Normal HTTP pages are not encrypted.
In this tutorial, i will explain how you can enable HTTPS to your account. Just as an added security measure.
1)Login To Your Facebook Account.
2)Go To Account Settings.
3)Then go to Security Option.
4)Enable HTTPS (by selecting checkbox of secure browsing), and save settings.
5)When you login next time, you will see HTTPS in the address bar.