How do I access the Oracle ADF Desktop Integration tool to edit an object?

From the Actions list item of Edit in Spreadsheet available from a product proposal's Cash Flow tab, Cost table, or Revenue table and the Resources tab. It's also available from the Elements table.

In the open Excel file, you then can add, remove, or update data, depending on the source of the Edit in Spreadsheet action. If you started from the Cash Flow or Resources tab, then you can add, remove, or update content in the Excel spreadsheet. If you started from the Elements table, then you can only update content for the metrics that are already editable in the user interface of the application.