Your fish may not die, you need to get the tank cycled. Unfortunately you're guna have to do a "fish in cycle". This will mean exposing your fish to high amounts of Ammonia and Nitrite, but your fish may survive. Since your tank isn't cycled and you seem a little lost with what to do, here's a small list of some of the things you're guna need during your cycle, to give your fish the best chance of survival.
Dechlorinator: seachem prime is one I personally like, its concentrated so you use less than other brands and can be safely overdosed up to 5x the standard dosage. Try to get a dechlorinator that will detoxify ammonia (this is why I like prime)
Test kits: these are expensive but extremely important. Api master kit works well, and is much cheaper than some of the other kits - test kits are extremely important so that you know how far through your cycle you are, and if you need to add extra prime.
If you want to give it a go you could get some bottled beneficial bacteria there is a bit of speculation on how well these work, if at all.. Read up on them and make your own decision.
Also as justarn said, if you have a friend with an already cycled tank you could ask them for a tiny bit of their sponge, or a hand full of gravel to put in your tank to 'seed' your filter. Anything in an established tank will have beneficial bacteria (BB) living on it, just make sure that whatever you get from friends stays wet (in water from the tank it came from - NOT in tap water) until you get it in your tank, once the surface that the BB live on dries out, they will all die. If you search nitrogen cycle on Google you should find a lot of useful info.
Don't give up hope, with a bit of luck and a lot of research, your fish might survive. Good luck!