If the Pneumonia is not too severe then yes hot steam when breathed in can help alleviate the pneumonia symptoms and help you breathe much better.
Taking a steamy hot shower or sitting in the bathroom with the shower steaming can help with the breathing when it's hard to breathe with pneumonia.
Using a humidifier or vaporizer in your room at night and in your living room during the daytime can help keep moisture inside your lungs to help you breathe better too.
If the Pneumonia starts to get worse or doesn't go away within a week then it could be a more severe form of pneumonia and a doctors visit or emergency room, urgent care visit is required so you can get treated for the pneumonia and get some antibiotics.