If you are using a Mac in the FLRC, all of the "guest" logins have the duplex mode available. You can toggle between "Standard" and "duplex" from the PRINT menu that comes up when you print from any application:

If you need to set up duplex mode for the first time:

1-Select PRINT in any application (Word, Safari, e.g.).

2-Under COPIES & PAGES, select LAYOUT

3-Select the option under TWO-SIDED for LONG-EDGED BINDING:

4-Next to PRESETS, select SAVE AS:

5-Type in DUPLEX and click OK :

DUPLEX will now appear as an option on the PRESETS menu for all applications.