If you are new to OpenCms, the OpenCms demo server is a good starting point. The demo server provides a personal OpenCms installation exclusively for you. All you need to do is register with a valid email address. The demo includes a full-featured website realised with OpenCms' standard Mercury template. There is a also short tutorial available to get familiar with OpenCms' content edition features.
For all kinds of questions about OpenCms, contact the mailing list:
The official docker image is available on Docker Hub:
The TLDDoc for the OpenCms taglib provides detailed information on all available tags and functions. It is a useful reference when writing JSPs in OpenCms: