By default, you can see the following items in each tab:
Assigned work packages
Project Level documents
You can change the items you want to see by tapping the existing selection and choosing the required option from the list. For example, if you want to see not just the work packages you are assigned to, but all the work packages in your project:
Tap Assigned from the Work Packages tab.
Select All from the list.
You can see all the work packages now.
You can see all the work packages in the Work Packages tab only if you are a project manager or planner.