If your air mattress is leaking, first locate the puncture by inflating the mattress and listening for hissing sounds or feeling for air escaping. Once located, mark the area and deflate the mattress. Apply a patch or use a repair kit specifically designed for air mattresses to seal the puncture. Follow the instructions carefully, ensuring the patch adheres securely. Test the repaired area by reinflating the mattress and checking for any leaks.