I did play around with the letsencrypt SSL few days ago, taking me quite some times to get it installed.
First, you must make sure you have at least the Python v2.7.x or above, and also the virtualenv installed.
Install the letsencrypt.
cd /root
git clone https://github.com/letsencrypt/letsencrypt10
cd letsencrypt
./letsencrypt-auto
And if you get the following error, please refer to the link,
https://www.digitalocean.com/community/tutorials/how-to-set-up-python-2-7-6-and-3-3-3-on-centos-6-4, to get the virtualenv installed.
virtualenv: command not found
In fact, I still got the error (not virtualenv error, could not remember thou) when running ./letsencrypt-auto command. So, I did in manual method to generate the SSL.
./letsencrypt-auto certonly --webroot -w /home/your_domain/public_html -d your_domain.com -d www.your_domain.com
Then, copy the SSL into /etc/pki/tls directory.
cp -f /etc/letsencrypt/live/your_domain/cert.pem /etc/pki/tls/certs/your_domain.cert
cp -f /etc/letsencrypt/live/your_domain/fullchain.pem /etc/pki/tls/certs/your_domain.bundle
cp -f /etc/letsencrypt/live/your_domain/privkey.pem /etc/pki/tls/certs/your_domain.key
At your CWP, go to Apache settings >> SSL cert manager, on your right hand side form, choose the cert, user & enter your domain; then install SSL. Done.
Note: Make sure you have the 443 port open in firewall & listen to port 443.
You may test the score of SSL cert at
https://www.ssllabs.com/ssltest.
At the beginning, I got the score C and after did some researches, I added the following lines onto this file /usr/local/apache/conf.d/vhosts-ssl.conf.
....
SSLEngine on
SSLProtocol All -SSLv2 -SSLv3
SSLCompression Off
SSLHonorCipherOrder On
SSLCipherSuite "EECDH+ECDSA+AESGCM:EECDH+aRSA+AESGCM:EECDH+ECDSA+SHA384:EECDH+ECDSA+SHA256:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH+aRSA!RC4:EECDH:!RC4:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS"
....
Restart the apache.
I got the score A now.
Hope this guide will help you. Cheer.