The first question that comes up is: should defining the OKRs happen bottom-up or top-down? There is no wrong or right way in this case. In some cases upper management or the CEO outlines the company OKRs first and then asks team managers to set their team goals in accordance with the company ones, followed by personal employee goals based on team ones.
In other cases, all employees are asked to come up with suggestions for their next quarter’s activities. In both cases, you come together at the team level to reiterate them and add, delete, or modify some of them.
In the end the process moves both ways. You need to go over the company level objectives and personal objectives many times before they work well together.