The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
You get some airline tubing and put one end into your tank. Then put the new fish into a holding container (a small bucket or some such) and run the other end of the airline into the bucket with the new fish. Start a siphon (the easiest is to suck on the opposite end of the tubing until water starts coming out). Then either tie some knots into the tubing so the flow slows to a fast drip or you can buy some cheap air flow adjusters. Here's a quick video: