This is the time when you define how you will achieve the desired outcome of the project embodied within the objectives and definition of deliverables. Planning requires that the project manager decides which people, resources and budget are required to complete the project. You will need to decide if you will break up your project into manageable phases, decide which products will be delivered in each phase, and decide the composition of your project team. Since you have already defined the deliverables, you must decide what activities are required to produce each deliverable.
You can use techniques such as Work Breakdown Structures (WBS) to help you to achieve this. You will need to estimate the time and effort required to complete each activity, dependencies between related activities and decide on a realistic schedule to complete the activities. It’s always a good idea to involve the project team in estimating how long the activities will take since they will be the ones actually doing the work. Capture all of this into the project plan document. You also need to get the key stakeholders to review and agree to this plan.