Charging 6 NiMH batteries in series via solar
The panel will automatically limit the current to a safe 'trickle' charge, so all you have to do is connect it directly to the battery. 

If the panel has high dark current then a small Schottky diode in series will block the reverse current. Your panel probably has pretty low dark current so the diode may not be necessary, though it could be a good safety feature if the panel is wired remotely (a short in the panel leads won't short out the battery).