Public folders only work on Outlook for desktop and Outlook online.
Open Outlook on the desktop.
In the Outlook side bar, select the Folders icon. This is located in the bottom left hand corner and you may need to press the three dots.
Open Public Folders - [Your Email] at the end of the list in the sidebar.
Open All Public Folders.
Find the folder you want to add. Right click it and select Add to Favorites.
In the window press options:
Check both boxes.
Choose Add All Subfolders from both sections.
Click Add. This should add all current and future folders to the favorites group.
Now, click Favorites. This is a sibling folder (not a child) under All Public Folders. You should see your folders and subfolders.
Now, right click your folder and all subfolders and select Show In Favorites. These will now appear in the Favorites section of the left hand window/menu for the appropriate folders (email, calendar, contacts, tasks, etc.).
In Outlook 2016 for Mac, in the ribbon, select Tools tab, then click on Public Folders.
In Folder Browser window, navigate through the public folders tree until you locate the folder you need to access. Highlight the public folder, then click on Subscribe.
Note: You will need to individually subscribe to each public folder you need to access.
Open Mail in your Outlook 2016 for Mac. Under the Subscribed Public Folders you will see the list of public folder you subscribed to.
OWA (Outlook on the Web)
OWA is not as full featured as the Outlook Desktop Applications
Click here for the complete article on using Public Folders via OWA.