$ git clone https://github.com/letsencrypt/letsencrypt
$ cd letsencrypt
We are truly living in the best of all possible worlds. I remember going through this process 3 years ago and it was horrible. Now I was able to get it done in 10 minutes (including reading time for the directions).
One caveat: if you are going with the “force https” option during the configuration and your website is configured with http: in wordpress settings, you are going to lose your jetpack connection to wordpress.com. Change the address to https to be able to connect on wordpress.com again.