First off it's best to dilute it ahead of time in DISTILLED WATER NOT TAP WATER! That way its ready and disolved any time you need it. I don't know if it's necessary but I use a glass jar, I presonally use a mason jar, easy to find and cheap, or buy a glass bottle of something at the store and drink it and use it. Make sure to label it.
Anyway, if it's a 2 oz. pack of dry mix it with 16 oz. of DISTILLED water, then use 1/8 tsp. per gallon, so for 2 gallons 1/4 tsp. Good luck.