recommended for all ironware....never use soap to clean, never. Immediately after finishing cooking run very hot water into the pan & allow the pan to cool until you can use a scrubber of some sort, metal or plastic, to scour away any food residue. rinse pan well with hot water & allow to dry. some people then rub a light coat of mineral oil into pan but that is probably not needed for a seasoned skillet. you might check the Lodge website for any other information
Hot water and a plastic scrub pad. Let dry and wipe a little cooking oil on inside. Despite tutorials online that offer very complex multi step processes cast iron is actually very forgiving. Once seasoned and used frequently it is hard to do it wrong. It is OK to use soap occasionally. Two no-nos are avoid highly acidic foods. No tomatoes or vinegar etc. They will affect seasoning. Quick browning veggies for a frittata won't really affect it. Second, watch the temperature. Many recipes call for getting the pan smoking hot. Be careful. The only way to really screw up cast iron is to warp the bottom through overheating. It will take a lot of heat but is possible. My favorite 80 year old pan has a slight bow to it probably caused by my grandmother forgetting it on the stove once. Bottom line, best cooking system ever. Use it, and use it often.