Hi MK1985 and welcome to TFP!
The TF-100 kit works very well.
Use the vial with the white Chlorine sticker on it, fill to 10ml of pool water, use 1 heaping full of R-0871 DPD Powder, swirl well, should turn pink if you have chlorine, now add drops of R-0871 Reagent, each drop is .5 chlorine, swirling as you go, add drops until sample turns from pink to clear, if you went clear with 6 drops, your FC (Free Chlorine) reading would be 3.
Now add 5 drops of R-0003 Reagent, swirl to mix, if you have any CC (Combined Chlorine) it will turn back to some color of pink, if it does, add drops of R-0871 Reagent, swirling as you go and count drops to get back to clear, just as before each drop counts for .5, if you use 2 drops then you CC reading would be 1.
To get your TC (Total Chlorine) you add FC+CC= TC, in this example your readings would be:
FC 3
CC 1
TC 4
If your testing of FC was correct at .5, with a estimate of 6800 gallons of your pool size, the pool calculator said to add 78 oz. of 6% bleach to reach a target of 6 ppm chlorine for a CYA of 50 ppm.
I hope this helps you understand how to use this TF-100 kit and apply the results to the pool calculator to get the added amount of chlorine in your pool.
Chuck