Free-write without stopping every other minute to edit. You can edit later. Just get your story down within the parameters you set in your planning stage.
Refer to your outline and notes.
Your first job is to hook readers with a riveting lead sentence.
Your second job is to make readers care about your main character.
In the first chapter, introduce your protagonist and possibly your antagonist, plus key allies of each. But do not clutter your pages with too many different people. Create unique identities and speech for each so readers can easily tell them apart.