湯種面包的问题

1) if 4 cups of flour, how many cups or tablesppoon 湯種 I need to add?
2) why 湯種 has to be put into refrigerator to cool down before use?
3) what is the order to add 湯種 if I use bread machine? I always put liquid stuff first, then add dry stuff, such as flour. So should I add 湯種 along with liquid or dry stuff?

Thanks lot!