By default, you will only be able to view files and folders in Google File Stream that you have created yourself.
On the web version of Google Drive you can view files and folders that have been shared with you by clicking on the 'Shared with me' option which is listed in the left hand menu.
If you would like to be able to view these files within Google Drive File Stream, please follow the instructions below.
Step1 - Visit Google Drive on the web - https://www.google.com/drive/
Step2 - Sign in and click the 'Shared with me' section in the left hand menu.
Step3 - Select the files or folders that you want to view in Google File Stream and click 'Add to my drive'
Step4 - The selected files will appear soon after in your Google Drive File Stream.