Test the current cyanuric acid (CYA) level with a reliable pool test kit
Calculate how much CYA is needed to reach your target level
Buy cyanuric acid stabilizer or conditioner
Add the product according to the label instructions
Place the stabilizer in a sock or mesh bag if recommended
Hang the sock in front of a return jet or place it in the skimmer if allowed by the product label
Run the pool pump continuously until the product dissolves
Do not backwash or clean the filter immediately after adding CYA
Retest the water after 24 to 48 hours
Add more only if the level is still below target
Keep the CYA level within the recommended range for your pool type
Avoid overusing stabilized chlorine products if you do not want CYA to rise further