Since you don't have any livestock I would just use the water you mixed and put it into the tank. In the future though, after you have critters in the tank you preferably would want the salt to mix in the vats with a heater and a powerhead overnight and then use it the next day. Unless you are in a pinch and it's an emergency try to let the salt mix as long as you can.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.