It's easy to reboot the system from a SSH shell as user admin: just type reboot. But not so easy as a normal user from the desktop environment Xfce. There is no button or option to reboot or shutdown the system.

Add a new Item in the Panel (the area with the buttons on the bottom of the desktop). To do this right click in somewhere into the Panel and select Panel > Panel Preferences in the context menu.

Add a new Item of type Launcher. A Launcher can be configured to execute an arbitrary command. Hint: the Action Buttons item doesn't work for rebooting the system, the button will be grayed out.

The last step is to add a new empty item to the Launcher and configure them. To reboot the system use the command /sbin/reboot, add a name, maybe a comment and a nice icon to complete the Reboot Button.