System tray will not work on Vista 64 bit.
Otherwise, you can either go to the "Dock Contents" section in your OD Properties dialog box and choose "Display system tray icons along with my icons." See the first screen shot below.
The other option, which is the one I prefer, is to create a dedicated tabbed dock for the sys tray. Go to "My Docks," Choose "Create new tabbed dock." Click "Add Tab" and choose "Add a system tray tab." Then I prefer to remove all the other tabs. See the second screen shot below.
Hope this helps.