Moth Balls

I recently bought 2 new winter coats at a clearance sale. I read an article that said you should store them with moth balls, so I bought a box. Now I'm not sure how to use them correctly. The directions on the box aren't very clear. I know they're not suppose to touch the coats and that they're suppose to be airtight, but do you put the moth balls in a separate bag and then put them in with the coat? Please help.
Diane C