So I love all their comments, and highly suggest you follow them.
If you have any questions about any of the instructions, click the link to read more:
lowering ph & raise CYA: on recommend chemicals page
How many gallons is my pool & how much chemical do I need to add?
(Ignore this paragraph if familiar with muriatic acid) If after reading about Muriatic Acid (MA) you decide that's how you want to lower ph, great choice btw, then read this, especially comment #3 (by duraleigh) which describes my preferred way to add it. Never had a scare or accident following those instructions. A little wind blowing away from you towards the slow pouring acid is perfect. If there is no wind, a small fan or just holding your breath and taking breaks are my go to precautions so i never smell it, and thus don't breathe it.
Friendly reminder, add the calculated ph lower chemical with pump running, brush bottom to help mix thoroughly, wait 15 mins, retest ph, ( it is possible that it still tests above the max of your test kit after 15 mins. That's okay, just add same amount again, no need to recalculate, brush, retest in 15.)if ph went down but not all the way to 7.2, re calculate how much to add and safely add that amount. Brush, wait 15. Retest/recall/add/brush/ test until 7.2 is achieved.
Ask any questions at all that are not answered in pool school. Answers are often very fast.