I believe that currently the free plan does not include the ability to install an SSL certificate. However, you can use Cloudflare as an SSL proxy, which I currently do with my own site here. X10Hosting free plans do support Cloudflare Railgun, which encrypts all the traffic between Cloudflare and X10. So if you set your site to use Cloudflare as a proxy, then you can enable Cloudflare's Flexible SSL and Railgun, the combination of which will give your site users encrypted connections from their browsers all the way to the web server (with the caveat that Cloudflare can see the traffic because they are the middleman, but I trust Cloudflare).
Hope that helps.