Importing an Opt-Out list does not create contacts in your HubSpot database or count towards your billable number of contacts. Instead, it marks the email addresses on the list as ineligible to receive emails from your account. These email addresses will be included if you ever export a list of bounced and unsubscribed contacts (Content > Email > Export Unsubs and Bounces).
Navigate to Contacts > All Contacts
From your HubSpot Dashboard, navigate to Contacts > All Contacts.
Start your importClick Import in the upper-right hand corner.
Now you're on the Imports Dashboard. Click Start a new import.
Choose your import type
Select An opt-out list as your import type.
Choose your .csv file
Click Select a file to browse for your file or drag the file into the window.
Once the file is selected, click Upload.