We can always use help answering questions at Let’s Encrypt Community Support. See this blog post about why community support contributions are so important.
One of the best things you can do to help Let’s Encrypt is to contribute to community-maintained ACME clients.
You can help improve this website via its GitHub repository, including documentation and translations.
Our server-side CA software, Boulder, is open source. It’s based on the ACME protocol, and written primarily in Go. A great place to start is with the list of ‘help wanted’ issues and the contributors guide.