The pane to the left is the edit pane. You can use markdown language for easy formatting. The edit pane will default to the list of fermentables, hops and yeast in your recipe. Feel free to overwrite this to keep notes about your brew session. Issues that came up, substitutions added, etc.
The pane to the right is the view pane. This will be updated in real time as you type in the left pane.
Toggle this option on for auto saving your notes every 60 seconds.