The "Notes" module is exactly just that.
Put detailed notes in here for you and your team to view.
Title your notes in the top right so you can reference it from the main canvas.
The editor is capable of holding images and other rich HTML content to let you document what's necessary for your plan.
To tie it all in, assign checklist items and create comments for yourself or your team mates to collaborate together and get your plan ready to launch.
Click the red X at the top right to get back to the main canvas and continue planning.