Install

$ sudo apt-get update
$ sudo apt-get install software-properties-common
$ sudo add-apt-repository ppa:certbot/certbot
$ sudo apt-get update
$ sudo apt-get install python-certbot-nginx

Get Started
Certbot has a Nginx plugin, which is supported on many platforms, and certificate installation.

$ sudo certbot --nginx

If you're feeling more conservative and would like to make the changes to your Nginx configuration by hand, you can use the certonly subcommand:

$ sudo certbot --nginx certonly

Automating renewal
The Certbot packages on your system come with a cron job that will renew your certificates automatically before they expire. Since Let's Encrypt certificates last for 90 days, it's highly advisable to take advantage of this feature. You can test automatic renewal for your certificates by running this command:

$ sudo certbot renew --dry-run