I recently added some. I put the sock in the skimmer first, but since I have my pump on low and only 50% of the water goes thru the skimmer, it wasn't dissolving very much after 24 hours. So I moved it to the return, and it dissolved within the next 24, the water flow by the return was much better.
Ditto, wait a week to test, but after 24 hours after it's done dissolving, assume it's in there. So if you added enough to target 50, assume your CYA level is 50 and adjust your FC levels according to the CYA chart.