SSL (https://en.wikipedia.org/wiki/Transport_Layer_Security) is used to create an encrypted link between a browser and web server. This prevents eavesdroppers from snooping on the traffic between the two. Think of it as a tasty tortilla keeping the inner ingredients of your burrito a mystery. Is it chicken or three bean? Only the chef and customer can know for sure.
You already have SSL enabled on your dashboard. To enable SSL for your blog, visit your blog settings and turn on "Always serve blog over SSL" in the Encryption section.
SSL and themes
Keep in mind that enabling the option for a theme that wasn’t developed to support SSL may cause “mixed content” errors. If your blog looks weird after you turn SSL on, some resources that the theme needs to render itself may not be getting loaded. See below for more information on how this can be fixed by the theme designer. In the meantime, you can try out some of the other lovely themes in our Theme Garden.
SSL and custom domains
Unfortunately, because SSL relies on certificates that are associated with the site’s domain, we don’t currently support it for custom domains.