We recommend storing your tofu in a fridge for max 2 weeks of receiving it chilled. Once opened, if you do not finish the whole pack then there are 2 ways in which you can look after your tofu until your next dish:
Either a) drain out all the water and store for 2 days in a sealed ziplock bag or tupperware. b) cover completely with water, and change the water daily for upto 3 days. Both methods work so whichever you find more convenient.