A tough situation for you, I would be sure to let the tank sit empty for a few weeks and even do a few water changes in case the fish brought in disease. In the meantime there are some great videos online and be sure to find a reputable fish store where they can answer questions. Testing, especially in the start of a new tank is very important and you cannot use freshwater kits. Saltwater is a true learning experience but for most of us it is well worth the journey. Read, watch videos and talk with other reefers...