Install EPEL-Repository first, then you can install certbot.

sudo yum install certbot
# if you get an error about Requests
sudo pip install --upgrade --force-reinstall 'requests==2.6.0'

When using apache install the SSL Modul

yum -y install httpd mod_ssl python-certbot-apache

Automating renewal

Certbot can be configured to 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

If that appears to be working correctly, you can arrange for automatic renewal by adding a cron or systemd job which runs the following:

certbot renew

More detailed information and options about renewal can be found in the full documentation.