Hatching should happen in about 10-14 days, but I would be surprised if this batch actually hatched -- it is very common for clowns to eat the first batch, as most of the eggs aren't fertilized correctly.
But, lets assume that they will hatch, at this point there is nothing you can do, they will hatch and will either be eaten or be sucked into the filter. If you are really interesting in rearing the fry you will have to set up another tank, and raise food for the fry. It is a fairly time consuming project.