Blot up as much urine as possible with paper towels or a clean cloth
Remove bedding and wash it separately
Mix cold water with a small amount of mild detergent
Dab the stained area with the solution using a clean cloth
Blot again with dry towels to lift moisture
Sprinkle baking soda over the damp area
Let the baking soda sit for several hours
Vacuum the baking soda off the mattress
If needed, apply a solution of equal parts white vinegar and water
Blot the area again with clean towels
Let the mattress air dry completely
Use a fan or open windows to speed drying
Repeat the process if any smell or stain remains