How to Use Flonase, a nasal spray containing fluticasone, is used to treat nasal congestion, sneezing, and runny nose caused by allergies or other nasal conditions. To use Flonase correctly, prime the spray, insert the nozzle into one nostril while closing the other, and inhale while spraying. Repeat in the other nostril and avoid blowing your nose immediately after. Follow dosage instructions provided by your healthcare provider.