If you just want a free cert, you can use my letsencrypt-nosudo client[1], which doesn't ask for your private key or sudo access or have to be run on your server (except for one copy-paste line you can inspect). The official letsencrypt client is geared much more towards someone who doesn't understand how TLS certs work. For people who know what they're doing, you can use lightweight clients like mine to just get your free cert.

[1]: https://github.com/diafygi/letsencrypt-nosudo