Click Mail in the navigation bar at the top right of the screen
Right click on your name at the left of the screen and select add shared folder
Type the name of the person who has shared a folder with you in the search bar and click add
Their name will then appear on the left side of the inbox homepage with the list of shared folders they have shared with you. If that person has not shared any folders with you, you will be able to view their name on your inbox screen but will get an error message when you attempt to view folders. In this case, you should contact the person who has attempted to grant you access