Need help from those that got their dresses profesionally perserved...

After the wedding, I had the dressed cleaned and it had been hanging in my grandmothers closet for the past three years. I just brought it home and want to put it away so it doesn't turn yellow... how did the cleaners do it?
Should I cover it with a dark bag and put it in a box? Do I need moth balls (yuck)???

I'm going to try it on now and then I want to put it away. Thanks!