well it would be smart to quarintine them first, but of you want to add them quickly heres what to do- first float the bag they came in in your existing tank with the bag still closed. this is to get them acclimated. then after about 20 minutes, open the bag and hang it inside the tank still floating in the water. clip the bag onto the side of the tank with something. start adding water from your tank into the bag every 10 minutes. add about 3/4 of a cup each time. once that bag with your new fish is full, take the bag out. get a mesh net and go to a sink. pour the water from the bag through the net untill all of the water is out of the bag but the fish are still in the bag. ( make sure none of the water from the bag gets in your aquarium) quickly take and release your fish in the tank. there ya go! then turn the lights off in the tank until tomorrow morning so they dont get too stressed. goodluck!