Start doing lots of water changes- do an 80% one to start with, followed by a 30-40% ones for every day after that to help reomove as much salt as posible.
You should put your fish into a bucket of some sort. Have new water that has sat out for a day with the correct amout of salt in it wonce you have the fish inthe bucket put the new water in the tank and float the fish for about a half an hour.
You guys....wouldn't a major change in salinity shock the fish even more? If it were me I'd change no more than 50%. 50% less isn't gonna do anymore harm than what 100% has already done.