Your gonna need to remove the back panel of the freezer section, this diagram should help. When you get it off, you will see your evaperator coils, now the drain hole should be at the bottom. You will need to remove the ice from the floor, and locate the hole. You can use a hair dryer to help melt some of the ice, then get a turkey baster and some hot water and shoot the water down the hole until it is free of obstruction, it may take a while, so be patient. Once you clear the drain your problems will be gone, good luck and ask if you nedd more help.