Balls don't need to soak, although you may want to occasionally if they have a stuck shed or if they like to wallow around in their poo.

To soak them, place them in a tub filled about 1/2-3/4 up their sides with lukewarm water. If the water feels warm to you, it's probably too warm for your snake. Also, make sure you place the tub in their cage as the water can cool down quickly.

Here's a recent post with pics on soaking a Ball for stuck sheds.