How do you collect ashes in Pokemon emerald?

When the Ash Guy (Huff Puff ) (Haha) gives you the bag you are automaticly using it. Just walk through all the Ash you want. If all the Ash there is not enough to buy a Flute or furniture then go to a city and then go back and all the ash will be there again and you can start collecting it again. Keep doing that until you have enough Ash to buy what you want.