Hi Jessica,
To get the Submittals to appear in the Project Timeline, you will first have to import them into the project in the Submittals activity center by using the “Submittal Utilities - Import Spreadsheet” task. The excel spreadsheet will have to be formatted in a certain way, which you can find by clicking on the “How do I import existing or expected submittals from Microsoft Excel?” common question in the Submittals activity center.
Once the Submittals are imported, you can view them in the Project Timeline by switching into the Journal view in the Project Timeline activity center. When you select a date range in the timeline, submittals from that date range will appear in the list below the timeline.