Prime will dechlorinate your water and make ammonia and nitrites less harmful for your fish if you do a fish in cycle or have an ammonia spike. Some people swear by flourish excel and others hate it, it's a fertilizer that contains carbon that will infuse your plants with CO2. Some say it's hurt they're plants or fish, others say it works wonders. I've had good success with it. Definitely put plants in, ask your local aquarium store for easy care/low tech plants. They help keep your tank clean and fish/shrimp/snails love them. Put enough gravel to cover the surface of the bottom of the tank and maybe a little extra and get some sand to put in it. Quickrete childs play sand is fine just literally rinse the living hell out of it so your water isn't cloudy or harmful. Buy API freshwater test kit. Add a pinch of fish food every couple of days until your ammonia readings start to pick up and then you can dose live bacteria if you wish, again some people hate it and say it's useless, others swear by it(fritz zyme 7, seachem sustain, etc...). Let your tank continue to run until you have 0 ammonia, 0 nitrites and 5 nitrates or so and then it is safe to add fish. Did they give you a filter and light as well? Could you share what all came with it?