Is that all the equipment you have now? How about lights? Do you want to do a few larger fish or a lot of small fish?
190 gallons is a nice size tank. If you are trying to keep it simple the FX6's will be fine. If you don't mind complicating things a little a sump is something to consider.
Assuming that the equipment you listed is all you have I would get a refractometer meter(measure the salinity), a few power heads, heater and salt. By me salt is much cheaper at LFS then it is online.
Optional items will be a skimmer and a auto top off. If you go sumpless you will need a HOB skimmer. If you go with a sump your skimmer options open up a little more.
A auto top off. As water evaporates the salt stays in the tank. This causes the salt concentration to increase as you lose water to evaporation. An Auto top off will fill your tank with freshwater as it evaporates.
1) Set up the filtration.
2) Fill the tank with sand if you are starting off with dead sand. If you are starting off with live sand do not add it.
3) Add salt, one 200 gallon mix of instant ocean salt should be fine.
4) Fill the tank with water. I close the end of my hose half to increase the pressure. I use this to help mix the salt. If you have sand on the bottom it might not be a great idea. I use sink water, many people use RODI water. It is one of those never ending arguments I don't give me opinion on, so you can look into that yourself.
5) Turn on power heads and let the water mix for a few days.
6) Use your hydrometer to make sure the salinity is at the right levels. Check the water temperature. If it is all good it is time to start your cycle.
7) Add your rock and start your cycle. Some people like to start with live rock some with dry rock. You can cycle with live rock, bottle ammonia or decaying food.
This will be the only time you should be mixing water in the tank. Once you have livestock in the tank you need to mix the salt in a separate container, such as a garbage bin and then do you water change.