These two resources that you have access to are different ways of receiving email that isn't assigned to a staff member's account. The easiest way to tell the difference between these two is to look at the icon next to the name in the address book. Look at the below image to see the difference. You must be given access to either one of these types of accounts by IT for the steps below to work.
The single person icon next to a Name in the address book signifies that this entity is a shared mailbox.
The folder icon next to a Name in the address book signifies that this entity is a public folder email account.
This information is important when you need to add either one of these types to your Outlook. This article discusses using the "New" Outlook and the different steps that are followed for this newer version.
If you don't have the "New" Outlook then you can install it by going here or if there is a slider button at the top right of your desktop Outlook you can move the slider button and the "New" Outlook will be installed.
You can always return to the previous version, at least until Microsoft discontinues it, by typing Outlook in your Windows search bar.
Now that you have the application installed you can use the steps below to add a shared mailbox or public folder email account to this "New" Outlook
Right-click the name of your account in your left pane and select the applicable menu item depending on the type of account that you want to add.
Shared Mailbox
Enter the name of the account as shown in the address book or the email address and click on the applicable account when the search finds an account. Click on the Add button.
That is it, if you have been given permissions to this account then you will see the account in the left pane of the "New Outlook" in the Shared with me section, you will need to click on the arrow to the right to expand this folder. If you don't see it, you may need to either compress the Folders item or you could scroll towards the bottom of the left pane. You will need to use the arrow next to the account to expand it to see the inbox and other folders.
Public Folder
On the next screen you will need to navigate to the location of the public folder as shown below;
Once you get to the desired public folder then highlight it and click on Add Public Folder at the very top of the screen. You will see this public folder in your Favorites at the top of the screen if it is an email account. If it is a calendar, then you will see it in your list of calendars in the calendar area of Outlook.