The Docker image contains Ubuntu Linux with Isabelle2017. It can be used, e.g. on another Linux host like this:
docker pull makarius/isabelle:Isabelle2017
docker run makarius/isabelle:Isabelle2017
That provides command-line access to the regular isabelle tool wrapper, with indirection through the Docker container infrastructure.
The image already contains ML heaps for Isabelle/Pure and Isabelle/HOL. Here is an example to build more:
docker run makarius/isabelle:Isabelle2017 -s -b HOL-Library
Note that Docker is mainly for command-line tools on the “Cloud”. There is presently no Isabelle Prover IDE support, although very old-fashioned X11 connections can be made to work with extra tinkering.