The printer you wish to use with RDC must first be installed in your Mac or Windows environment.  If it is already then proceed to open RDC.  Before connecting open the preferences.

Choose the 'Printers' control panel.  From here you can select your printer.

Choose your desired printer.   If you are connected to a session you will have to restart RDC for the new printer to work.  Otherwise everything should be all set.