It depends on how rusted it has become. If it's very rusted you may need to have it sandblasted and just ReSeason it,
what can u do to one that has gotten rusted?
if it's just a light rust coating you can probably wipe it out with vegetable oil and ReSeason it again making sure to coat it very well.
You should Always "WASH" cooking utensils including cast iron skillets, just avoid using scouring pads or brillo pads and
make sure you heat the cast iron skillets on a stovetop to dry them thouroughly before storing,
It's best to store them in the oven but make sure you remove them when you use the oven..
Democracy is two wolves and a lamb voting on what to have for lunch.
Liberty is a well-armed lamb contesting the outcome of the vote.