This is a procedure to install and set up acme.sh on CentOS 6.  This replaces the previous method "certbot" which is no longer supported on CentOS 6.

First, install socat:

{{{
# yum install socat
}}}
Install acme.sh

{{{
# curl https://get.acme.sh | sh
}}}
This will create a hidden folder called ''.acme.sh'' in your home directory that will contain all of the files, certificates, and keys needed for certification.

Next issue the certificates for each site. Replace ''/path/to/your/webroot'' with your actual path. For example:

{{{
# cd ~/.acme.sh
# ./acme.sh --issue -d shop.gwcox.com.au -w /var/www/html/gwc0x --server letsencrypt
}}}
Install the certificates

{{{
# ./acme.sh --install-cert -d shop.gwcox.com.au --cert-file /etc/acme/shop.gwcox.com.au/cert.pem --key-file /etc/acme/shop.gwcox.com.au/key.pem --fullchain-file /etc/acme/shop.gwcox.com.au/fullchain.pem
}}}
This will install the certificates to /etc/acme/shop.gwcox.com.au (use a more appropriate directory name).  Next, you will need to add SSL version of the lines to your /etc/httpd/conf/httpd.conf

First make sure you have the following lines:

{{{
LoadModule ssl_module modules/mod_ssl.so
Listen 443
}}}
Then duplicate your <Virtualhost *:80> lines and change 80 to 443.  Add the SSL lines

{{{
<VirtualHost *:443>
    ServerAdmin webmaster@gwcox.com.au
    DocumentRoot /var/www/html/gwc0x
    ServerName shop.gwcox.com.au
    <Directory /var/www/html/gwc0x>
        Options FollowSymLinks MultiViews ExecCGI
        AllowOverride Options
        Order allow,deny
        Allow from all
    </Directory>
    SSLEngine on
    SSLProtocol all -SSLv2 -SSLv3
    SSLCertificateFile /etc/acme/shop.gwcox.com.au/cert.pem
    SSLCertificateKeyFile /etc/acme/shop.gwcox.com.au/key.pem
    SSLCertificateChainFile /etc/acme/shop.gwcox.com.au/fullchain.pem
    SSLCACertificateFile /etc/acme/shop.gwcox.com.au/fullchain.pem


    ErrorLog logs/shop.gwcox.com_SSL-error_log
    CustomLog logs/shop.gwcox.com_SSL-access_log common
</VirtualHost>
}}}
Restart apache

{{{
# service httpd restart
}}}
Use an online test site to test, such as https://www.ssllabs.com/ssltest/