Once the documents and content are up and ready for your users, you simply need to open the doors. How you do this however has a lot to do with whether your investment in SharePoint will be successful.
Are your users ready for SharePoint? Your staff may need additional training. Or, it may be best to start with a small set of pilot users; or, roll out one department, then slowly bring in other teams. This is part of the user adoption strategy described in the planning phase, and here is where it gets implemented.