From the Audience page click on + Add and select 'Add new members via CSV upload'.
This will open the CSV upload UI for you. In here there are three steps to upload your audience:
Upload the file
Match the file columns to Orbiit data fields
Review and correct any issues in your data.
NOTE: The CSV file should, at a minimum, have the following information: first name, last name, and email address (in three separate columns). If the Community Manager/Builder has access to additional information on the member (e.g. Company Name, Role, and LinkedIn account), it is advised to include in the CSV upload. The more information loaded prior to registration, the more time saved for the member. When they fill out the registration form, this information will be auto-populated. Members can still edit populated details if needed.
After closing the upload interface should now see all new members within your members list.