In Windows 7 and Vista you could do this by clicking START, WINDOWS SECURITY and then RESTART. Apparently WINDOWS SECURITY link has been removed from Win8 sooo I can think of just two ways to easily reboot a Win8 machine from an RDP session:
- on the tile page type RUN (select APPS on the top right) and click RUN, then enter:
shutdown -r -f Reboot
shutdown -f Shutdown
- Press ALT+F4 (i.e. close) and then select RESTART or SHUTDOWN
I hope this helps.