Your next step is to create a Work Breakdown Structure (WBS) that explains who does what and when. The WBS should also include any Phase Gates (review points as you come to the next phases of a project) and Key Performance Indicators (KPIs) telling you if you've achieved your goals in any particular phase.
That WBS gives you what you need to plan Time, Cost, and Resources. Then you can give team players their Work Task Packages, explaining specifically what each of them must deliver and how.
There are other super-important dimensions of project management that often get overlooked: management of Quality, Communications, Risk, Procurement, and Stakeholder Engagement.
With so many things going on simultaneously, the Project Manager is there to Monitor + Control the process, and to Integrate the work of the entire team.
Now, of course, nothing ever goes as planned. Change is the only constant. Therefore, every good Project Management Office (PMO) has a Change Management protocol in place to make sure there’s no Scope Creep or unforeseen risk. As we say, “If you fail to plan, you plan to fail.”
Once you reach the end of your project, there is still one important process to complete: Closing. This is the formal wrap-up and it includes documenting Lessons Learned for the benefit of future projects in the same organization.