How long to wait to swim after adding cyuranic acid?

First of all don't add solid stabilizer to your skimmer. It can clog your skimmer and take a long time to dissolve if in your filter.

Use the sock method. Put the stabilizer in a sock and hang the sock in front of a return jet where it will get some water flow passing over it. Squeeze the sock every few hours to release the CYA.

You can swim while adding the CYA.