Here are the instructions:
Capitole MkII:
Press the remote CHannel up button and hold it for a couple of seconds.
The display will show Balance L / R in db.
Adjust balance with the Volume up and down buttons.
Press CHannel up/down buttons to return to default CD display (# of tracks, time)
Capitole Reference:
Press Menu on the front panel; Balance will appear on display; Use Volume up and down buttons to adjust balance; press Menu again to return to default CD display (# of tracks, time)
Enjoy!