Wait to get the package until your tank is cycled.
As has been said above. I would take the damsels back to the fish store for 3 reasons. 1) You shouldn't cycle your tank with live animals you are essentially putting them in a vat of poisen and hoping they will survive. 2) If they do survive they will be a menace on all other fish you want to put in a tank. 3) A 58 isn't that big for a saltwater tank, you won't be able to add many more fish if you already have 6 fish in there.
If you have live rock (which is essential to a saltwater system) you shouldn't need to add fish to a system to cycle it.
Also, it's suggested that you only add 1 or 2 fish at a time to let your tank catch up to the extra bio load and they dominance dynamics settle in.
I would start by reading the Concientious Marine Aquarist if you haven't already read a book on saltwater keeping.
-Good luck, trying slowing down a bit to make sure you are making the best decisions...