Using Let’s Encrypt to secure your site

Lets add the certbot repository:

sudo add-apt-repository ppa:certbot/certbot

Install Certbot’s Apache package with apt:

sudo apt install python-certbot-apache

Now use Certbot to obtain the SSL certificate:

sudo certbot --apache -d your_domain -d www.your_domain

This runs certbot with the --apache plugin, using -d to specify the names you’d like the certificate to be valid for.

If that’s successful, certbot will ask how you’d like to configure your HTTPS settings:

Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access.
-------------------------------------------------------------------------------
1: No redirect - Make no further changes to the webserver configuration.
2: Redirect - Make all requests redirect to secure HTTPS access. Choose this for
new sites, or if you're confident your site works on HTTPS. You can undo this
change by editing your web server's configuration.
-------------------------------------------------------------------------------
Select the appropriate number [1-2] then [enter] (press 'c' to cancel):

Select your choice then hit ENTER. The configuration will be updated, and Apache will reload to pick up the new settings. certbot will wrap up with a message telling you the process was successful and where your certificates are stored:

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/your_domain/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/your_domain/privkey.pem
   Your cert will expire on 2018-07-23. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot again
   with the "certonly" option. To non-interactively renew *all* of
   your certificates, run "certbot renew"
 - Your account credentials have been saved in your Certbot
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Certbot so
   making regular backups of this folder is ideal.
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

Finally lets test the certificate renewal process by doing a dry run with certbot:

sudo certbot renew --dry-run

If you see no errors, you’re all set.