The first step will be identifying the stakeholders. The larger the organization and project, the more stakeholders there may be, and the harder they may be to find. A great suggestion is starting from a responsibility assignment matrix, also known as an RACI chart, which is a project management tool to identify who should be responsible, accountable, consulted, and informed:
You can use different formats to build your RACI chart, such as a spreadsheet (probably the easiest format). On the racichart.org page, you can download their template. This is an example of how this would be filled:
You can also add the tasks in detail or ...