In the project configuration, under Build Environment, check the Run Docker commands on CloudShare VM box. This enables CloudShare docker-machines.
Optionally, in the Machine name field, you can modify the name of the VM that will be provisioned and dedicated to the project. By default, the VM is called
jenkins-$JOB_NAME. This default causes one CloudShare VM to be provisioned per Jenkins job.
Optionally, change the expiration period in the Days until VM expires field. By default, the VMs are deleted after 14 days. If you're concerned that even with that automatic deletion, you'll be accumulating too many unused environments over time, you could set it to something shorter.
If you change the docker-machine name to
jenkins-$JOB_NAME-$EXECUTOR_NUMBER, for example, you would get a separate CloudShare environment and VM per build. This could help you if you have Execute concurrent builds if necessary enabled in the Jenkins job and you don't want concurrent builds to run on the same VM, e.g. because you are publishing host ports during the build.