Acclimation is getting your new fish adjusted to your tank before you just put it in there, and it goes into shock. To do this you want to gradually get the fish adjusted. You need to take a bucket, and put your new fish in it along with the water thats in the bag with the fish. Take a small air pump and air stone and put the air stone in the bucket with the fish for oxygen. Take another piece of air tubing and tie a knot in it. Put one end in your tank the other in the bucket. That one will be your siphon adjust the knot so its only dripping a couple drops per second into the bucket. You will keep your fish in the bucket for at least two hours you want the bucket to be at least 4 or 5 times fuller than what you started with. You may have to put a small heater in the bucket to keep it at your tanks temp. After this you can add the fish to your tank. Keep the lights off in your tank for a couple hours also for the fish to adjust. I would also recommend dumping the water from the bucket and filling the tank back up with new. I hope I worded this ok and its easy for you to understand. Good Luck