Once you have the top management support for the project, sou should conduct a gap analysis to determine to what extent your organization is already compliant with ISO 13485 and what needs to be done to achieve full compliance. After determining the gaps, you can define the project plan for the implementation where you will define the activities, documents to be developed, responsibilities and deadlines.
Usually, the first step in the project is defining the procedure for document and record control, and then the quality policy. The next step is to identify the processes and resource management. Then you can conduct risk assessment and define controls for the processes.
Once your processes are set up, you can perform internal audit and management review and you will be ready for the certification audit.