That information is incorrect. With the exception of properly contained Bio-Spire (sp) and a few other select products which people have reported success, your tank is not ready for fish as of yet.
You can cycle the tank with fish in it, however, if not properly maintained during this period, you can expect additional fish loss as well as harmful living conditions for those that survive.
Get an Aquarium Pharmacuticals Master Freshwater test kit and maintain ammonia and nitrite levels under .25 ppm
until you see them disappear completely and only nitrates present in the tank. At this point the tank will be fully cycled.
Prime is a product intended to remove chlorine and Chlormines from tap water as well as eat up SOME ammonia and other harmful toxins to your fish. During this cycle period however, its ability to stablize the water will be overwhelmed by the amount of ammonia and nitrite in the water.
If you do a test and the levels are above what i just posted, all that is necessary is a partial water change 25-50% with new fresh tap water. Be sure to add more prime. The cycle will take anywhere from 4 - 8 weeks maybe long due to the cycling with fish and constant water changes.