First mistake--NEVER believe most LFS. Most of them only want to make money. The more that dies in your tank, the more they sell you and often the people working there are not qualified. Most of the time I would never recommend putting chemicals in your tank. The best thing you can do is move very slowly, let things happen naturally, and do alot of research yourself while you wait. If the petstore that has the fish coming in is the same one that gave you this terrible advice, I would have a serious conversation with them and have them sell the fish to someone else or hold them for you. If they realize they could potentially make alot of money from you in the future, they might be a little more flexible. You should not be adding fish at this point.
Premade salt vs. making your own salt has nothing to do with cycling. I'm not sure how to link prev. threads but if you look under the search, there is a really good thread by Spanko explaining cycling and why it is so important. Pretty sure Beth and Bang Guy have some great info also. It is better if you use a dead shrimp to cycle your tank rather than live fish. The clowns might make it, but unlikely that the wrasse will.
Typically you can expect about 6 weeks (give or take a couple) to complete a cycle. Then you still need to move slowly. This is a wonderful forum to learn and ask questions.