It is recommended that you wait a couple of months for the newly poured concrete steps to cure before drilling commences for the new handrail. However, it does depend on the time of year. In the winter, the newly poured concrete steps will take longer to cure due to the damp, cold weather. However, in the summer, the sun will speed up the process. Alternatively, you can take a note out of the contractor’s book and bore holes for fasteners in the concrete steps after a week. Just bolt this in place with epoxy and the following day install the handrail. This will give good results, but will not be as strong as it would have been if the steps had cured.