Exporting project schedules from Office Timeline to Excel is a simple process that uses the Copy Data feature which is built into the product. You can access it from the Milestone Wizard or the Task Wizard.
From your timeline, click on the Task (or Milestone) button on the Office Timeline ribbon. Once on the Task Wizard, hover your mouse over any Task to make the Menu option (3 dots) appear. Click on the menu options and select Copy data. This will copy all of your Milestone data and your Task data to a clipboard.
Now open Excel and paste.
Here's a video that will help you get started with the Excel Import: