When adding new fish into the tank, you should do the following:
1) Let the bag flow in your tank or sump for at least fifteen minutes. This will let the bagged water temperature equivalent to the water temperature in your tank.
2) Pour out 1/3 of the water in the bag, then adds 1/3 of the tank water into the bag. Wait fifteen minutes; repeat this until all the water in the bag is your tank water. The whole process should be around forty-five minutes.
3) Release the fish and shut the light off. The light should remain off for the rest of the day to prevent stressing the fish.
HTH!