Fill the tub with water from your garden hose. If you have it a pre-filter that fits on the hose would be good. Your dealer should have one. Take a sample of the water with you to the dealer and ask for a recommendation for how to get it right.
You will want your total alkalinity to be around 140-150 ppm, pH 7.4 - 7.8. 3-5 ppm for dichlor. The amount of chemical to add to reach these levels depends on the water you start with and the capacity of your tub. That should be about it. If you have time go to
www.rhtubs.com and get the water treatment outline from the Vermonter. It will outline the whole deal very well.
BTW, your dealer may put the big press on you to use the BaquaSpa instead of dichlor. Decline politely but firmly.
Regards,
Bill