Hi Kellydee,
I'm new too, and I did exactly the same, the shop gave me 'beneficial bacteria' (which doesn't work) and said after two weeks the fish could go in. I lost 2 lots of Cardinals, 7 in total with 1 remaining, having been told by the shop it was my tap water which killed the first lot!!! It's not the tap water at all, it's all down to getting your filter filled up with good bacteria the proper way. And that's the 'Cycling' CezzaXV is talking about.
These fish shops are utter sharks (pardon the pun) and I'd love to know if anyone on these forums have ever been told by a fish shop about fishless cycling? The only advice I can give you is to read, read and read some more in all the beginner threads on these forums. I've learnt loads in a couple of weeks, feel horribly bad that some of the problems I've had could have been so preventable, but know some/most of this is due to bad advice from my local fish shop (lfs).
Good luck and keep us updated.