Quite often, systems need to be rebooted. You can, of course, login to do that or you can do it from the portal.
From you virtual machine's detail view, clock on "Reboot Virtual Machine" on the far right panel.
Or, from your browser view, click on to reboot your VM. You will be asked to confirm this action.
Note: When a restart is issued, the system tries to do so gracefully. Any sessions or activity will, however, be interrupted.