If you're connecting your Exchange/Office 365/Outlook address book from the Contacts+ for Mac app, click on Contacts+ (menu dashboard at the top of your Mac), click Preferences, then click the icon at the bottom left corner. If you're connecting your Exchange/Office 365/Outlook address book in the Contacts+ for Web app, you can do so from your Sync Sources. How can I connect my Exchange/Office 365/Outlook address book to my Contacts+ account?
Microsoft: Exchange / Office 365 / Outlook