To edit your Subdocument, in the Project Details page, select the Subdocument of your choosing in the Side Menu. This will launch the a preview page where you will notice a small preview of the Subdocument is present in the preview window.
Figure 1: The Subdocument preview window.
To open the Edit Section window (online editor), select the edit button in the tool bar.
Figure 2: The edit button is located in the tool bar.
To edit your Subdocument, use the options provided in the tool bar of the Online Editor to make the necessary edits.
Figure 3: The Subdocument open in the Online Editor.