How soon can I paint the wood?I'm buying it either from Lowe's or home depot where the wood is kept indoors.. thanks

For paint, give it 6 months. With stains, it varies since they do not block moisture movement. Some can be applied immediately.

For more reading on it, see
Treated Wood - Arch Wood Protection, Inc. - Maintenance Tips

I agree w/ rickj. Even though its indoors it is soaked due to being indoors. The wood doesn't get to dry out like it would if it was being stored outside under protective cover/roof.