I'm sure that the seeds are already in the soil there from the previous growth, but if you feel obligated to do something, you could go ahead and plant some fresh seed as soon as the frost danger has past. They should be planted in full sun. The soil shouldn't be too fertile or moist because those conditions tend to stimulate production of foliage instead of flowers. Fertilizing should be kept to a minimum for the same reasons. You may also start the seeds indoors in 3-inch peat pots four to six weeks before the last frost is due and then plant the pots directly into the garden when you can be sure they won't be killed off by a late frost.
Success is unlikely if the seeds are started in flats because morning glories resent transplanting.