To communicate with your unassigned contacts, start by navigating to the Office-wide account through the user switcher toggle. Then navigate to the Campaigns menu.
From here:

• Click Create Campaign.
• Within your Recipients module, click Browse
  
• Click on the Audiences tab.
• Tick Unassigned.
• Click Apply.
• Then complete your campaign, e.g: add Date & Time and Send Email modules.

* If you would like to replicate any campaigns already saved in your User or Admin accounts to send to your unassigned contacts, contact Support for assistance.