From here you may transfer your site from one phase to the next as explained in Three Phase Workflow
Transfer the site from the Develop phase to the Demo phase.
If it exists the version currently in Demo will be saved before the trasfer.
Block all users to prevent changes to the site while maintenance is performed.
Once the cycle is completed and the site is published the users will be unblocked automatically
When you block all users, all active sessions will be closed and the UNSAVED changes will be lost.