Ask the same question to your seller, to have his advice with its zapper.
Generally speaking, I will start zapping anywhere for some time (no more than 30mn continuously, to begin with). Sometime could be a couple of days or a couple of weeks…
When you will reach a steady level where nothing happens any more, for at least 5 to 7 days, try for 1h with the red (active) output closet to your liver, and your black output on a sane area (your hand or your foot will do)