The next step depends on the result of the evaluation and interview. If the result turns out to be quite bad, you should first justify the reason for the appraisal. After that, explain the specific areas in which the employee needs to improve and how to do it. It's like a mentor-mentee intervention.
If the appraisal result is commendable, you should assess the areas where the employee performs well and coach them on how they can excel further if they maintain the performance. Always keep in mind how you, as an appraiser, influence the performance of your appraisee.