Install Let's Encrypt - SSL Free Certificate.
Let's Encrypt is a certificate authority that launched on April 12, 2016 that provides free X.509 certificates for Transport Layer Security (TLS) encryption via an automated process designed to eliminate the hitherto complex process of manual creation, validation, signing, installation, and renewal of certificates for secure websites.
How to install Let's Encrypt
With Shell Access
The best way to install Let's Encrypt from shell is by using CertBot client https://certbot.eff.org/