Gather the Mylar balloon, a straw or balloon pump, and string if needed
Locate the inflation tab or valve at the bottom of the balloon
Insert the straw or pump nozzle into the valve
Blow air in slowly or use the pump to fill the balloon
Stop when the balloon is firm but not overly tight
Remove the straw or nozzle carefully
Pinch or press the valve closed to seal the air inside
Attach string if you want to hold or display the balloon