Get a bucket and put some pool water in it. Measure out the acid and pour it into the bucket with pool water. ALWAYS ADD ACID TO WATER!!
Never add the water to the acid. Also, be careful not to inhale the fumes, it is nasty, nasty stuff! Ask me how I know.
Then take the diluted mixture and pour slowly in front of return.
I usually give it like 15 mins before adding the bleach. Never mix bleach with the acid either, that is REALLY bad.
As long as you are only adding enough acid to adjust within range (7.5 - 7.8), then you should be fine waiting like a half an hour or so to swim.
You can check your ph level again after 15 mins.