Moister in headlight, how do you remove and can you reseal it

These are not fully sealed housings.
They have two vents on the back side.
However, if the rubber seal on the top that covers the seam for the front and back is poor/leaking, that leads to too much water getting in to vent out.
Inspect integrity of the housing. Make sure everything is sound. If something looks like it might allow water to bleed in, use some silicone sealant (heck, even duct tape) to cover the area.
Inspect the vents and make sure they are not blocked somehow.
Give it some good, hot summer days in the sun (I know, we all need some of those) or drive with the lights on to heat up the housings and vent that moisture out.

Pyrophore is leading you down the right path. The clear plastic lens part is not fully sealed against the black plastic housing or the vent or bulb socket boots are leaking. You can run a bead of silicone along the lens to housing joint after you dry the headlight out. You can remove both the bulbs and blow warm air into one and vent out of the other bulb opening. Do not put the hair dryer on high though since that will damage the lens. Good luck