If you have a list of email addresses from another address book source, you can bulk add these to your address book. Before you begin, extract a comma-separated list of email addresses from your external source of contacts.
To bulk upload email addresses
Click your avatar and select profile, then select the address book tab.
Click the plus icon – this is where you can add new email addresses either one-by-one, or in bulk.
Paste the comma-separated list of email addresses, then press tab.
You can find more address book tips and tricks here.