You need to take the bulb access panel off the rear of the lights, then blow a heater or hair dryer at the lens until the condensation clears. If there are actual droplets, chances are there could be more water in the light unit and it'll just return. If that's the case try blowing hot air into the light unit through the where the panel goes on. Anyway, leave the lights a little while then replace the panel. It's best done on a dry day. If there's rain or humidity in the ,the air you trap inside the light will be damp and when the headlight lens cools (e.g. overnight) condensation will re-form. If this happens you can remove the panels and drive around with them off but for goodness sake put them back before it rains!
Of course none of this stops water getting in in the first place. On my GT water seems to collect on the top of the headlamp and run down the back of the unit on to a conveniently located tab, where, if the seal between the panel and the light were anything less than watertight, water would creep in.
2004 '54 GT JTD
1984 Alpina B9 (my other love)