Splunk Cloud runs Splunk as a service, so you don't get access to the CLI. If you want that level of access consider running Splunk yourself either on-prem on in the cloud. There is a Splunk AMI in the Amazon marketplace you can use.
In Splunk Cloud, if you need to do something from the CLI (i.e change a setting in a .conf) you would file a support ticket as a change request and it would be processed.
If you use Splunk Cloud, you will get essentially enhanced power user level access on the GUI but no ssh access.
Features that could impact the service have been grayed out. But you can do some admin stuff as that user, like edit props.conf (via Sourcetypes in the GUI) and create other users.
Check out the Splunk Cloud release notes for more info: http://docs.splunk.com/Documentation/SplunkCloud/latest/RelNotes/NewSplunkCloudFeatures
Shell access is not available (to external consumers of Splunk in the cloud). More and more actions that require shell access in core Splunk will be provided through the GUI over time. What is it specifically that you are attempting to accomplish?
As khourihan mentions, you wont get access to the SSH. Most of the admin functionality you can perform from the current GUI of cloud, anything outside of that you need to contact support and open a request for them to do it.