[Chlorine and MPS at same time?]

So I’m new to hot tub and I’m having a hard time with all this. So I’m using Spa fusion sanitizer and spa chlorine free shock treatment. We have had the hot tub 4 days so it is seeing a lot of use. Up to four people at a time(2 adults 2 kids). Currently I’m having a hard time with chlorine. Everything else is spot on. What I’m doing now is adding both chlorine 1.5 teaspoons for 2 person use with 2 teaspoons of mph after use. Should I be adding both at same time? Also next day I read very low chlorine on test strip. Comes up white

[How do you add you granular chlorine?]

Just looking to see how people add the granular chlorine and other chemicals. Does everyone just add straight into the water? Does everyone add it to through the filters system?