OK, so you bought the tank today and didn't have a plan for the fish. May not be random, but was still avoidable.
Either way, the point is to keep them alive and in good health. They should be ok in a reasonable sized container of saltwater with a bubbler and heater while you redo the tank. Fish are not demanding creatures. The salinity should be the same as the salinity of the water they were in, and the temp should be close also, and they need air.
Or, take them to a local saltwater fish store.